Ghast

Ghasts are very large jellyfish-like mobs that float through the air and shoot fireballs from their mouths. Its body is a 4 by 4 by 4 block cube with 9 tentacle-like limbs hanging from the bottom. They first appeared in the Halloween Update. Ghasts are able to spawn anywhere in the Nether, as long as there is sufficient space.

Behavior
Ghasts normally float around with their eyes and mouth closed. They open their eyes and mouth when attacking. They make a chirp-like noise when shooting and scream loudly when taking damage. The sounds that Ghasts make have a minimum intensity regardless of their distance, so they often sound closer when they are actually far away.

If a Ghast's fireball hits a portal (or close to it) the portal will be closed, requiring re-ignition. If the player manages to get a Ghast to fire at the portal while it is closed, it can be reignited using the fireball. Blocks originally ignited once struck, adding an extra hazard to fighting Ghasts; however, the fire is extinguished immediately afterwards because of a bug.

The minimum block resistance required to absorb all blast force of the Ghast's fireballs is 20.17, meaning that fences and other less resistant blocks will be destroyed in a fireball explosion.

Ghasts will not fire at the player without line-of-sight, and this is blocked by glass, leaves, portals, or webs making safe scenic paths through the Nether a viable possibility. When not moving, Ghasts within firing range will face the player, giving the impression that they can see through transparent materials. Ghasts can draw line-of-sight through curtains of lava, and their fireballs can pass through it meaning players near a pillar of lava can be struck without seeing the source.

Ghasts drop Gunpowder when killed, but this can be hard to collect - as it is the only mob that flies, the gunpowder may fall into lava or an inaccessible area.

Ghasts may give birth to creepers at a 0.003% rate, causing the creeper to drop down from the current height of the Ghast, mostly dropping it in lava. as can be seen here

Fighting Ghasts
Ghasts attack with projectile fireballs. The player can reflect these fireballs by hitting them with anything before they impact, even bare hands, arrows or fishing rods. It is possible to kill Ghasts by reflecting their attacks back at them. Although rather tricky to pull off, you can make this easier by shooting an arrow, fishing rod, or snowball at the fireball, then looking directly at the Ghast, or where it will be in the next second or two, and it will send the fireball in that direction once hit. This way, if a Ghast is out of reach from your projectiles, you can "aim" its own fireballs back at it, instead of having to run directly at the ball to fire it in the right direction. The Ghast hitbox includes the tentacles, so aiming for the area where the tentacles meet the body increases the chance of a hit.

Ghasts may be hurt with normal weapons if the player can get close enough or has a bow and arrows. It is possible to use a fishing rod to draw Ghasts in near enough to hit with a sword. A close Ghast is also easier to hit with a bow, though the drawback of this method is less time to dodge fireballs. When aiming your bow be sure to lead your shots as Ghasts can quickly change trajectory and move quite fast. Depending on how far away the Ghast is it may be necessary to aim above the Ghast as well to gain extra range.

Ghasts are often considered the hardest mob to kill. Due to them being so common this makes the Nether a hard place to survive in. Ghasts can also break blocks from under the player, often dropping them into lava or causing death through falling damage.

Ghasts may also be set on fire, but fire and lava don't actually damage them. A similar effect is seen with zombie pigmen. When a Ghast is caught in lava, its movement is impeded, and then they can be easily targeted by arrows.

Much like using neutral or enemy mobs as shields against arrows fired by skeletons in the regular world, it is feasible to use zombie pigmen as shields against Ghasts in the Nether. It is possible to injure or kill zombie pigmen in this fashion without ever making them hostile to the player.

It is disputed that Ghasts can be killed by lava or fire if continually re-exposed. This is achieved by a Ghast floating in and out of lava. There have been reports of zombie pigmen dying while in lava, due to the fact they "bob" in and out of lava, which raises doubt that Ghasts and zombie pigmen are completely lava/fireproof.

Despite being fireproof, Ghasts and Zombie Pigmen are capable of drowning if under water or lava for too long. This means they, like the player and other mobs, require air to live.

Drops
Beta: (However Difficult to Obtain.)
 * 0-6 units of Gunpowder

Trivia

 * Ghasts can "cancel" their fireballs if the targeted player has an obstruction between the Ghast and themselves.
 * Ghasts aim at the camera, not the player. Going into 3rd person mode and having a Ghast fire a fireball at you will go over the player, given the right camera angle. This also means that they will continue to fire at the player if they are dead, but is still in the respawn/quit window.
 * Ghasts can cause other monsters to attack it but it will only attempt to attack the player.
 * If you manage to hit a ghast with its own fireball, it is dealt very little damage compared to the damage done when it hits a surface, another mob, or you.
 * If you successfully reflect a Ghast's fireball, and if you "aim" right, you can get the fireball to strike and kill a Zombie Pigman, without even making them hostile.
 * Ghasts are not affected by light, and thus appear the same brightness anywhere.
 * When a Ghast shoots a fireball in the real world it looks like a flaming snowball, though it doesn't have effect like a normal snowball.
 * If the cursor is over the Ghast's fireball the box around the equipped item will light up.
 * Notch added a small chance for Ghasts to spawn in the Overworld near Portals in Beta 1.5. A Ghast spawned outside of the Nether will fly everywhere, mainly above the clouds.
 * Ghasts are the biggest mob, being twice as big as the biggest varitation of slime.

Гаст