Ghast

The Ghast is a floating jellyfish-esque mob that shoots fireballs from its mouth. Its body is a 4 by 4 by 4 block cube with several tentacle-like body parts emerging 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. While an extremely rare occurrence, ghasts may spawn near portals in the regular world if given enough space to do so.

Ghasts normally float around with their eyes and mouth closed, making a sound like cooing children. 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 are currently not affected by distance, so they always sound very close, regardless of their actual position.

Netherstone and imported dirt blocks can be destroyed by the Ghast's fireballs. Netherstone will burn forever once struck, adding an extra hazard to fighting Ghasts. Items that are placed directly on walls, such as ladders or buttons, can also be destroyed or dislodged. Materials that cannot be destroyed include
 * Cobblestone
 * Stone
 * Diamond
 * Iron doors
 * Obsidian.

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.

Ghasts will not fire at the player without line-of-sight, and they cannot see through glass, leaves or portals, making safe scenic paths through the Nether a viable possibility. Ghasts can see 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 floats, the gunpowder may fall into lava or an inaccessible area.

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.

Ghasts may be hurt with normal weapons if the player can get close enough or has a bow. 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.

Ghasts may also be set on fire, but fire and lava don't actually damage them. A similar effect is seen with zombie pigmen.

It is disputed that Ghasts can be killed by lava or fire when exposed to it long enough. There have been reports of zombie pigmen dying while in lava, which raises the question of if ghasts and zombie pigmen are completely lava/fireproof.

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.

Drops
Alpha:
 * 0-2 units of Gunpowder

Trivia

 * Ghasts can be seen on the map when using a map editor