Tutorials/Multiplayer PvP bases

A server with a factions plugin installed plays quite differently than most any other server. In factions servers, players team up to dominate the map. This can lead to some epic fights, as well as much fun. However, players that are new or are simply uninformed can be quite befuddled by the different play-style as it adds several new mechanics. Often with people in enchanted diamond armor camping spawn, all blocks within a 10,000 block radius of spawn inhabited, and most of the resources within a 20,000 radius stripped bare, simply getting started can be a nightmare. But never fear! With the right knowledge, and a little bit of luck, you too can create a dominant faction that can rule the map!

Starting Out
Time: 60–120 seconds

As soon as you enter a server for the first time, type /f list into chat. This is a command that will list the factions that have been made. There are normally 10 factions per page, and subsequent pages can be viewed by placing a number after "list". However, just worry about the first page. First off, note how many pages there are. The more factions there are, the further you must travel to reach uncharted territory. A good rule of thumb is 1000 blocks per page of factions. Secondly, look at the top three factions and take note of their membership and numbers. The numbers represent, respectively, land claimed, current power, and max power. If the current power is 0 or negative, then you can claim over their land. If the land claimed is 0, then they have no territory (though they still probably have some basic gear). This isn't necessary for where or how far you want to go, but such information is always handy. Most servers also give players a set of stone tools (although some give far more than that) to start with. If you don't have anything, then type /kit. If that doesn't give you anything, then /kit starter or /kit basic should work. If it doesn't, then that server doesn't give any tools to beginners. No problem, you just have to do without.

Ask people online about the largest factions (normally the top 4 or 5 on the f list) and who is fighting who. Typically there will be a large conflict with the two largest factions, or a smaller faction who is determined they can take on the world and the other factions are united against them. This info will prove useful later when you need to make allies, enemies, raid and conquer.

On the road again...
Time: 30–60 minutes

Once you have information on the factions, as well as your set of starting tools, it's time to head out. If anyone is anywhere near spawn, start sprinting in the opposite direction or don't leave spawn until they leave your view range. Either way, you should be good/safe after a couple hundred blocks of running. At this point, stop sprinting to conserve your hunger. Just walk the distance (this WILL take a while!) that's recommended for the number of factions. As you hike, make sure to do all of the following:
 * Kill ALL animals you find.
 * Harvest any wild sugar cane and pumpkins.
 * If a village, temple, etc., is found, ESPECIALLY near spawn, completely ignore it. There is a good chance that everything is looted, the villagers are killed, and the town is griefed. If you want to spend your time on it, go ahead, but it probably wont have much to salvage.
 * Grab up to a stack of cocoa beans if you travel through a jungle.
 * If night comes, then you may or may not keep traveling. Some servers have as many or more mobs than single player to make up for the amount of players killing them. If you think you can handle the mobs then keep moving, but if not, then you can dig a 3 block deep hole for yourself in the ground, jump in, and put a block over your head. You can then wait all night, or disconnect from the server and do something else for 7.5 minutes.
 * Make sure you have as many seeds as you think is necessary for your ambitions and at least one sapling. You don't know what resources your home will have.
 * If you come up to an ocean, it may be a good idea to build a boat at this point, because swimming is even slower than walking. With a boat, however, travel time can be cut in half.
 * Ocean travel is generally superior to land travel anyway. If you come across an ocean, even if you have to turn 90 degrees to go across it, then you should try to get across because you will make much more distance. You travel faster, you don't consume hunger (very important!), and you don't have to deal with mobs or players.
 * If you keep walking, eventually you will have to deal with a world border. On most servers, there is a point around 5000 or 10000 blocks on server which nothing can go past. This is to encourage raiding so people don't keep walking for millions of blocks and never get raided. It is important to not make a base right on the edge of the world border. Many people find faction bases by walking around the very edge of the map, so it would be smart to stray away from the very edge.
 * If any higher ranking players want to "help you" or "give you stuff", they most likely are going to kill you. Either politely refuse or ask them to bring the items to a safe place such as spawn where they can't attack you and use a sethome or /back to get back to where you were.

Choosing a Location
Time: 0 seconds - 1 hour

Once you have reached your recommended distance, it might be worth it to keep travelling depending on where you are and what your ambitions are.
 * If you're in the ocean, you should usually keep going until you find land. However, if you already have everything it might be better to make an underwater base in the middle of the ocean (discussed later). *Strongholds can be used as good bases. They allow for potentially exclusive (if no one has found the other two strongholds, or if the other two strongholds have been destroyed in an...unfortunate TNT accident) and easy access to the end, contain a plethora of books to put into an enchanting room, and your base will be already built and most likely secluded without you even having to lift a finger!
 * Check in on what plugins are in use on the server by doing /pl, or if you don't have permission, ask a high ranking staff member or the owner. Different mechanics, such as a guns plugin or a steel mod, can greatly change the worth of resources and you must double check it before settling on a place.

There's a few recommended setups you can go with listed below. Dinky wooden houses that you might build on singleplayer worlds or PvE servers won't cut it in the savage world of Factions PvP, and many a newcomer has been destroyed because of their lack of knowledge on proper base building. You have to be stealthy and fortified. Read the list below and see which one appeals to you and your location the most:


 * 1) A vast above ground stronghold. These are best for well established factions that have the power and resources to build large above ground fortresses and claim the entire base and the land surrounding it. If these are your ambitions, it's recommended that you travel to a plains or snow plains biome.  If this applies to you, then skip to part I of the bases guide.
 * 2) A floating skybase.  Most places are good for this, but this design will not function well in biomes such as jungles, mountains, or other places with high elevation, as other players will be able to see your base easier.  If this applies to you, then skip to part II of the base guide.
 * 3) An underground bunker.  Just about anywhere will do, but don't go down via caves as miners venturing down into the caves will come across your base all too easily.  In addition, digging from the bottom of the ocean down will almost guarantee that your base will never be found.  If this applies to you, then skip to part III of the guide.
 * 4) An underwater base. Obviously, you'll need an ocean. It takes a lot of hard work to get one started up, and you'll probably drown a few times, but once you get it going it will be hard to raid as TNT work work on the outside and anyone who tries to dig into it will probably drown. If this applies to you, skip to part IV of the base guide.

Total time spent in Part I: 31 minutes to 3 hours

Planning
Time: 0–5 minutes in Minecraft, 5–15 minutes offscreen

You have a bunch of food from all those animals you killed, you have a source of trees and wheat, you have a bed, now you need somewhere to put it all. Not so fast! The most crucial part of any project is planning, so spend some time off the server wracking your brain for what you want. Do you want a large, proud base with redstone traps at every corner, enough wheat capacity to feed a small nation, and all the bells and whistles? Or do you want a smaller base that can easily be hidden under a hill? Do you want walls of obsidian that are immune just about anything, or cheaper cobblestone walls? All factors must be thought of before deciding to build a base. Maybe you could even log out for a moment, get a spare sheet of paper and actually design out your base so you have some type of idea of what it shall look like. Graph paper works well for this because you can plot out individual blocks.

Terraforming
Time: .5–3 hours

No matter what your plan is, you're going to need flat land, and lots of it. Stone shovels are the best tool for clearing out tons of dirt, since they're quick, cheap, and easily replaceable. Likewise, stone pickaxes are best for the odd clump of stone. First dig out the perimeter of your base, then start digging in. Keep a lookout for hostile mobs or even other players that have tailed you - extreme distance is a good defense, but it's not infallible. Also, make sure to plant that sapling, and use some bonemeal to grow it quicker if you have any bones. By the time this is done, you should have a TON of dirt left over. If the server also has a shop plugin, great - all that dirt you dug up is probably worth a couple of diamonds. If not, then keep it on hand just in case. You never know when a cheap, unburnable, gravity-defying filler material will be useful.

Physical Defenses
Time: 1-nearly infinite hours

You've got your area—now it's time to secure it. There's three types of defenses: Active, Passive, and Hybrid. Active defenses actively try to kill any threats posed. This could be people in your faction defending against the attacking enemy, landmines, fall traps, arrow dispensers, etc. They are usually activated when a threat is within range and lay dormant when they are not. Passive defenses attempt to stop potential threats before they become threats. These usually are obstacles rather than deadly things. This might include iron doors, cobwebs, walls, stacks of gravel, and the location of your base if it is somewhere hard to get to. Sometimes active and passive defenses come together to form Hybrid defenses, which are, as you might have guessed, a combination of an active and passive defense. This could be lava inside a wall to flow out when someone tries to dig through, checkerboarded holes with landmines inside, and many other creative combinations. When designing your defenses, strive to have mostly hybrid defenses, and have a good balance of active and passive defenses. A base with fully passive defenses will eventually be gotten through, and if your base has only active defenses it will be so easy to get into that the attrition of enemies will eventually exhaust your active defenses. This isn't to say that ALL your defenses should be hybrid, but MOST of them should be.

Here's a few pointers on defenses:

Passive

 * You have a ton of dirt, but that's nowhere near good enough for a wall. At minimum, you want multiple layers of cobblestone.
 * Now's a good opportunity to start a shaft mine or even a quarry. If you want a self-building wall, make sure to get at least 4 stacks of redstone and a couple of stacks of iron to build the pistons and wiring necessary.
 * Obsidian may take a long time to obtain, but it will be worth it. If you don't have diamond tools you can use buckets of lava and pour water on them where you want them to be placed in a technique called molding. If you have the area claimed, obsidian walls are practically impenetrable through use of TNT or trying to dig through, unless a plugin on the server has changed it.
 * Another trick for your walls is to put sand or gravel inside them. This will make them somewhat self-repairing as if someone attempts to blow a hole in your wall, or dig through it, the sand or gravel will keep falling down and replacing the ones they break. It won't stop them, but it might delay them long enough for you to scramble your defenses.

Active

 * Minefields are a good idea. Get a bunch of stone, build a load of pressure plates, and place them all around your base. You can make a fake minefield (it is also good for spotting invisible players) if you aren't planning on making that much TNT to bury in the ground. It will be a great bluff as the mere thought of that many explosives under their feet will scare away just about anyone, and they will never know that it was fake. If you do go putting TNT under the ground, it's recommended that you surround it with water. It will still damage entities but won't make big craters in your base.
 * Dispensers with arrows or fire charges can be hooked to pressure plates or tripwires to weaken or even kill your enemies without you lifting a finger.
 * If you're expecting an imminent and immediate raid, if you have the manpower it may be a good idea to keep your faction members on patrol around the base. You can run drills and make sure that your faction can work efficiently and cooperate as a team if the base falls under siege.

Hybrid

 * Put lava inside your walls for a deadly surprise when they try to dig through.
 * Cactus can be a hybrid defense in themselves: They work as both an active defense by pricking anyone who comes too close, and a passive defense by acting as an obstacle or barrier if you set them up that way.
 * Cobwebs can be put over a hole with lava directly beneath it to catch and burn players.
 * Hybrid designs are a matter of creativity and ingenuity. You can experiment and find new combinations and there's just about infinite ways to combine and defend.

Getting Ready For the Rest of Forever
Time: ???

At this point, you've gotten past the limits of this guide. Your adventure to be the top dog is up to you now. If you still don't know where to go, then some suggested steps are:
 * Expand your mine and keep hoarding diamonds and iron.
 * Use your spare cobblestone to make an experience farm.
 * Sell your spare stuff you don't need instead of letting it clog up your storage space.
 * Create a faction armory with at least 1 reserved set of armor and weapons for each member.
 * Go to the Nether to acquire the resources there
 * Recruit people into your faction to speed the process up as well as improve defensibility
 * Pick a side in whatever is the large conflict is to gain stronger allies and to have someone to fight.

Total time spent in part II: 2-8.5 hours Total time spent in total: 2.5-11.5 hours

II. The Flying Base
So, you want your base high in the sky. Well, there are some pros and cons to this idea.

PROS
 * People will strain their eyes trying to see your fortress.


 * If someone tries to get inside via a pillar, you can smack them off and probably terminate them.


 * If it's well lit, don't expect attacks from interfering mobs.


 * if made out of chests and trapped chests, it is completely undetectable without a hacked client


 * It's nearly impossible to access.

CONS


 * It's nearly impossible to access.


 * You won't be able to have a shaft mine or a quarry.


 * One wrong step while patrolling the exterior means you can have fun trying to get back up there... WITHOUT anyone seeing you.


 * It's pretty easy to see if you look at it right.


 * There will be a huge shadow under your base, so someone right under it will know what's going on. To disguise the shadow, make a small decoy house with torches around it. Put basic items inside to improve the deception. The torches around will hide the shadow and look natural this way. If raiders come by they will loot the house and go on, and not even suspect to look up and see the huge loomed fortress above!

If you REALLY want to proceed with this, then continue.

Picking a Spot
Selecting a spot for this is hard. As previously stated, don't make this thing in an extreme hills or jungle biome. If it's high enough over an ocean, plains, desert, etc.... then it will take a while to notice and often be obscured by clouds. If it's over an extreme hills or jungle, anyone getting materials from a tree or climbing a mountain will look up and see your precious base sitting there as inconspicuous as the last doughnut at a policemens' meeting. You don't want that. Instead, build it over a valley... in a plain... below sea level. That should help disguise your place.

Getting Up There
This is pretty hard. You want to get up in the sky. You don't want anyone to know you're in the sky. Your only real option is to pillar up there. But how will you get down? The answer: sethomes.

Most, if not all factions/pvp servers, allow you to set a "home" that you can return to at any time. If this is one of those servers, you can skip the portals and instead type /sethome (or /f sethome to set your whole faction's home), and /home (or /f home) to return to the exact point you used /sethome (or /f sethome) at. Set your home up in the base, and then have a pool of water to fall into right below your base. Then, when you want to get up, just type /home!

If you don't have f homes or sethomes, never fear...
The answer for you? Nether transport! First, get enough obsidian and/or molding supplies to make two portals. Next, make sure there's no one in a 100-block radius of your soon-to-be base. Then, pillar up about two hundred blocks: not really necessary, but it's a nice height. Sure, you can't really see the ground, but people will need a LOT of dirt to get up there. After that, make a Nether portal up there. You then want to go about sixty-four blocks away from your location. Make another portal. Go through it, and back in the Overworld, cover it up using dirt or something to make a convincing, small hill. Go back through your portal and make a walkway to easily get between your portals. You may wish to disguise it later, but it's fine for now. Go back through your sky portal and you'll end up on top of your pillar.

Once you're on top of your pillar with your preferred method of transport in place, build a few blocks off, smash your pillar, and make a small platform.

Building of the base
Now you've got a platform. You've got to build off from it to make your base. There's basically two approaches to this:
 * 1) You can go for the walled fort look. It makes pillaring from the side virtually impossible and its boxy shape will make it blend in with the clouds. But, it's more resource-intensive and cannons that shoot TNT upward at high velocities are exceedingly deadly, because with some aiming, they can shoot right onto your roof or platform. If you go with this method, you may want to consider covering the bottom with wool, snow, quartz or similarly colored blocks to blend in easier with the clouds.
 * 2) You can build a sort of "village" up there, with several separate buildings with no fully surrounding wall. It's not as resource intensive and is easier to expand. However, pillar raids are much easier than if there was a wall. Also, it's harder to maneuver around and a misstep can find you falling to your death. In addition, it is harder to maneuver and your bridges may cause you to have to take a more convoluted path to get from one place to another.

You may want to make a sort of (safety net) above and/or below the platform. This way, if TNT lands on the roof, then it will take extra TNT to get to the actual platform. The one underneath prevents you from falling and dying every time you walk along without paying attention to the terrain.

Whichever you choose, this kind of base is good because it protects you from your foes BEFORE they see you. Of course, it has weaknesses in the fact that it is tricky to set up in the first place and can be somewhat hard to defend, depending on how you build it.

To make it easier, build murder holes (holes in the floor that you can shoot arrows though). You may also want to build a few "outposts" around 50 blocks from the ground. That way, you can kill enemies easily. Beware though; if you build outposts, then it's a dead giveaway that there is a skybase somewhere around, so only build them if you have at least 2 chunks of land in each direction claimed and aren't worried about stealth.

Getting Ready For the Rest of Forever
Time: ???

At this point, you've gotten past the limits of this guide. Your adventure to be the top dog is up to you now. If you still don't know where to go, then some suggested steps are:
 * Have a hidden mine on the ground to obtain your diamonds and iron.
 * Make an experience farm, possibly in the End or find a spawner in your hidden mine.
 * Sell your spare stuff you don't need instead of letting it clog up your storage space.
 * Create a faction armory with at least 1 reserved set of armor and weapons for each member.
 * Get resources from the Nether such as blaze rods or quartz.
 * Recruit people into your faction to speed the process up as well as improve defensibility
 * Pick a side in whatever is the large conflict is to gain stronger allies and to have someone to fight.
 * Expand your farms to become self-sufficient. If you want to get animals up there, try putting water in a waterfall. Lead the animals into it and they will swim up.

III. The Massive Cave Base
For a video example of a massive cave base, check the embedded video below:

Keep in mind, this base was made on a server that has explosive damage and ender pearls disabled.

PROS
 * Can be hard to locate.
 * Easy access to ores and caverns.
 * Gain materials from digging out instead of losing materials from building.

CONS
 * Can be hard to find again if you don't have a sethome.
 * Can be difficult to get back to the surface.
 * Can also be easy to find if you're near a very large cave system (or even a stronghold)
 * Digging it out and get it running will take a very long time (and dozens of stone pickaxes)

Construction
The first thing to do is deciding where do you want to build your base. The best location would be an ocean, far away from the shore, but be way, as people can drop their render distances to glitch inside. Once you have located a good spot, create an airshaft and start digging down. You usually want to build the base at layers 10-20 so you can mine for diamonds easily. Get ready for LOTS of spare cobblestone, and you will eventually run into coal and iron, and if you're lucky, gold or even diamonds.

NOTE: Be sure to get as MUCH obsidian as possible, if you encase your base in obsidian, there is no need for an ocean. It is also in some ways better than an ocean due to the reader distance glitch and hybrid cannons.

First part: the core/main base
Once you are at a good depth, it's time to begin digging out the base. Don't start tunneling just yet! Dig out a square (4 blocks of height are recommended) big enough to contain all the basic rooms of the base (crafting room, enchanting room, forge, furnace room, storage room, and others). 25x25 should be more than enough, though you can expand it as you wish. Build walls and start decorating the basic rooms.

Second part: the outer ring/add-ons
Once your main base is established, then you can begin tunneling and expanding. What will you make a tunnel to is your choice. It can be a wheat farm (same design for carrot and potato farms), a tree farm, a mob grinder, a mine or quarry, it's up to you. Just keep in mind that you'll need to claim everything that you expand into or else other players can get into your base.

Third part: secret rooms/basements
This step is optional but recommended. It's a good idea to have a secret door that leads to a basement located at an even lower depth than your main base. There you can keep a secret storage room to stash your valuable resources in (be sure to leave some of your iron/gold/diamonds in the main base. If enemies break into your base and find no resources, they'll probably figure out there's a secret room), and also a library to store books containing information on enemies and their bases.

Getting Ready For the Rest of Forever
Time: ???

If all is done correctly, you'll have an underground fortress deep below, don't put it in the ocean, as people can use a low render distance to glitch into your base, instead, make a water wall, with hybrid defenses. Be sure to cover the air-shaft used to access the base, or disguise it to make it look natural, hiding the trapdoor. This can seem like paranoia but it's always good to have more stealth and safety. Your base will take a very long time to be found even if enemies are hunting you relentlessly.

At this point, you've gotten past the limits of this guide. Your adventure to be the top dog is up to you now. If you still don't know where to go, then some suggested steps are:
 * Branch out your mine and hoard all that precious iron and diamond.
 * Make an experience farm or grinder.
 * Sell your spare stuff you don't need instead of letting it clog up your storage space.
 * Create a faction armory with at least 1 reserved set of armor and weapons for each member.
 * Get resources from the Nether such as blaze rods or quartz.
 * Recruit people into your faction to speed the process up as well as improve defensibility
 * Pick a side in whatever is the large conflict is to gain stronger allies and to have someone to fight.
 * Expand your farms to become self-sufficient.

IV: Underwater base
Materials: fist, dry sponges, pickaxe (stone minimum) and torches if too far from surface, (optional: pistons, buttons, redstone)

Building the base: First, obtain some sponges. Either raid them from an underwater monument, buy them from the shop, or steal them from another person. Then, go find an ocean. A really big ocean. Then, go to the bottom and place down three sugar cane in a stack. You'll be able to breathe when standing in the sugar cane. Begin building your base above ground under the water. Don't worry about drainging it yet, just build what you want it to be. Go ahead and build more space than you think you'll need so that you wont have to expand and flood your base again. Once you have it completely built and sealed from the outside water, take those sponges and use them to drain out the inside of your base. You now have an underwater base!

To get out, you'll either have to use:
 * 1) A simple trapdoor or door. Albeit unsecure, it's the simplest way to get in and out and if you keep it hidden most players won't look for it.
 * 2) Nether transport. First, get enough obsidian and/or molding supplies to make two portals. Next, make sure there's no one in a 100-block radius of your base. Make a nether portal in your base and go through it. You then want to go about sixty-four blocks away from your location. Make another portal. Go through it, and back in the Overworld, cover it up using dirt, sand or something depending on the area to make a convincing, small hill. Go back through your portal and make a walkway to easily get between your portals. Go back through your sky portal and you'll end up back in your base.

An Ocean monument can make a good underwater base. All you need to do is to clear out the water using sponges, eliminate all three Elder Guardians and you got yourself an easy base! Most people won't bother to check all the monuments because there are quite a few. Also, the Guardians that spawn outside the Ocean Monument can act as a good shield against most basic players. However, certain players may try to enter due to the 8 Gold Blocks in the Treasure Room, which you should have already removed by this point. If you hear Guardians being damaged when you are not killing them, it is likely some players are trying the approach the Monument. Shoot at them with bows to try and keep them away, and the combination of the guardians' beams, your arrows, and their drowning will either kill them or damage them enough that they will stay away.

Underwater bases are great as they are entirely submerged into water, if any players want to grief it they have to either:
 * Using Sand or Gravel to block off the water, then try to TNT cannon in (which will take a long time and will alert anyone nearby, who will come out and defend against the players)
 * Ender Pearling (Which will still take a long time as Ender Pearls now obey normal Physics and drop straight to the ground once entering water, and if you have your base completely sealed it won't be a problem)
 * Using Sponges to remove water and TNT cannon in (The same ending for Situation 1)
 * Nether Transport (They CAN enter if they know how to do it, so break your inside portal when you're not using it and make sure to hide your portals well.
 * Find an entrance (which should be well enough hidden that they won't find it)

Protecting against Hackers
So, you guys want to try to protect against hackers, some of the most unfair players in a game. There are several options. Most of the options below are ways someone can protect against most hackers.

Xray Hack:

What you need: Depends, but at the most, some pickaxes, any large quantity ore, and dispensers/hopper/droppers/anything that can contain items but not be detected by ChestESP.

For Xray hackers, they can see into the ground, ignoring any stone entities, and can see any bases underground. This is mainly for underground bases.

What you can do: 1. Make it extremely small: bases are harder to detect by Xray-ers if they are small. So, try to make your base as small as possible. 2. Surround it with ores: Average hackers keep Xray on the same setting as normal. Which means that they can NOT see through ores. Surround your extremely small base with ores, preferably coal, with a silk touch pick. Try to make it look like a natural cluster of ores, not big or even shaped. Coal is recommended as it is in large veins. Also, try mixing the coal ores with other ores, preferably iron ore.

For ChestESP: The way ChestESP works is by detecting any chests around the Hackers viewpoint, a hack that can foil the Xray defence. But, it can't detect Dispensers, droppers, or hoppers, or anything that can store items. So, to protect against this, move everything you have in your chests into a storage compartment, anything above, or in your inventory. Ender chests are extremely helpful as well. Obviously this is not the best way to store things so if you feel confident in your base's security, you may just want to risk leaving your stuff in your chests.

For extremely experienced hackers: The tricks above will not fool the most experienced hackers, who had personal experience with these kinds of things. However, a way someone can ultimately protect against any players is to make a completely un-raidable base, like above. While tricky, tough to gain resources, and sometimes fails, if you know how to make an un-raidable base, you can survive nearly everything, except abusing OPs.

Final Tips
Keep these in mind as you become the top faction:
 * If you want to keep people not in your faction out of an area of your base, put doors in front of it. Allied faction members can't open doors unless they have pressure plates in front of them.
 * Read up on historical military strategies. Although they're from real life, many principles still apply to factions warfare and may just help you outsmart the competition.
 * Ally, ally, ally! You don't have to fight everyone. Make some friends as you go. Conquest is always more fun when it's shared with good friends.
 * Obsidian is essentially bedrock in claimed areas, unless the server has a plugin that lets it be blown up.
 * Your defense is only as strong as its weakest link. Any weak spots in your defenses WILL be found by your enemies, and it WILL be exploited so much it will boggle your mind. One missing block of obsidian or one mine that isn't claimed at the entrance and sealed off by a door can be your downfall.
 * You'll most likely forget to obsidian the floor when you're obsidian covering your base. It's an easy mistake to make. Make sure you do that.