Nether Reactor

The Nether Reactor is a built structure which, when activated, generates a room of Netherrack (7x17x17) with some openings around the reactor called a "Nether Spire" (unofficial name). It also turns the reactor itself, excluding the core, into Netherrack (or obsidian for iOS, confirmed for 0.6.1). At this point the reactor will begin to spawn various blocks and items, as well as Zombie Pigmen.

The Nether Reactor is built with a nether reactor core, 4 gold blocks, and 14 cobblestone, arranged in the configuration to the right.

Behavior
When the Nether Reactor is built and the core activated (by tapping), there will be a Client message that says, "Active!", and it generates a room of Netherrack (7x17x17) with some openings, around the reactor unofficially called a "Nether Spire". It destroys any block that happens to be in the way of the room. The blocks that make up the reactor, excluding the core, will turn into Netherrack

and it will start spawning various items and blocks. These can be gold ingots, melon seeds, paintings, Glowstone Dust, doors, both types of mushroom, bones, cacti, arrows, sugar cane, bowls, beds, bows, Nether Quartz and feathers, as well as Zombie Pigmen. After it burns out, there will be a massive Netherrack structure with multiple floors. The bottom floor is hollow (all blocks inside other than the reactor are replaced with air), and the upper floors retain the blocks that were already there (air for an above-ground spire, dirt/stone/etc. for an underground spire). The core is still there, and is reusable. The used core is found in a 3x3 obsidian box where the reactor was constructed. When the reactor is active, the core's texture will change to red, and after it burns out, it will change to a blackened texture.

The Nether Reactor only lasts around 45 seconds. During the 45 seconds the Reactor is active, it is easy to escape the room, as it is all Netherrack. Once about 5,10, or 15 seconds have passed, the time sets to nighttime, so left over items in the room can despawn once the Nether Reactor stops.

The Zombie Pigmen who spawn are hostile to the player, and will get hurt in sunlight, unlike the ones in the PC or Xbox versions. Their texture is also slightly different.

Trivia

 * The Reactor does not currently function in Creative mode; this is intended.
 * The reactor's structure was originally iron and gold blocks rather than cobblestone and gold, but this was changed due to its cost and the fact that the reactor turns everything into obsidian except the core.
 * The air blocks in the pattern are not optional. This means the player cannot build the reactor underwater unless you waterproof the air blocks in the pattern.
 * The player can quickly mine some or all of the materials out of the reactor after activation and it will still function. This way the player can recycle the expensive Gold Blocks. Another alternative method is to simply have someone else help mine the blocks right after activation. If they're fast enough, they'll have time to mine all four gold blocks with a diamond pickaxe before they turn to obsidian.
 * If the player constructs the reactor near a world edge and activate it, they will see it turn night.
 * There is an elevation limit for the reactor, above which it cannot be activated.
 * If the player wants to hide the spire produced by the reaction, they must build the reactor deep underground.
 * If the player wants the spire not to get "blown up", you can break the active core.
 * The spire makes a good mushroom farm due to the low light levels inside it. Mushrooms spread really quickly when in the spire.
 * It takes 36 gold ingots, six iron ingots, three diamonds, and 14 cobblestone to build the nether reactor.
 * The ONLY block the nether reactor can't destroy is the "invisible bedrock" on the world edge. Mainly because it breaks the netherrack (obsidian 0.5.0) before it spawns.
 * Do not put the reactor next to your house and other buildings, since it will destroy them.