Ghast

Ghasts are white, floating, jellyfish-like hostile mobs that live in the Nether and shoot explosive fireballs at the player. They are the second-largest mobs that naturally spawn in the game, the largest being the ender dragon.

Spawning
To spawn naturally, Ghasts require a solid block below them and 5×4×5 free space. They spawn only in the Basalt Deltas, Nether Wastes, and Soul Sand Valley, all three of which exist only in the Nether dimension, and in any light level. In Soul Sand Valleys, where only Skeletons and Ghasts spawn, Ghasts cannot spawn if another Ghast is within 16 blocks of spherical distance to the intended spawning location.

Ghasts do not spawn in nether fortresses.

Drops
. Looting increases the maximum ghast tears dropped by one per level, for a maximum of 4 ghast tears with Looting III.

. Looting increases the maximum gunpowder dropped by one per level, for a maximum of 5 gunpowder with Looting III.
 * when killed by the player.

Behavior
Ghasts float around the Nether with their eyes and mouth closed and periodically make crying sounds, opening their eyes and mouth when attacking.

They emit a loud screech when attacking the player. The sounds that the ghast makes have a minimum intensity regardless of their distance, meaning that they can sound closer than they actually are. They have a hitbox of 4×4×4 blocks, as well as 9 tentacles. The tentacles are not part of the ghast's hitbox.

Ghasts have a search range of 100 blocks, an explosive attack and mobility. Unlike most other hostile mobs, the ghast does not have a pursuit mode; it does not attempt to draw closer to the player when at long range and is likely to float away if it's in a large space and not killed quickly enough.

Ghasts can cause other mobs to attack it, but the ghast never targets other mobs; it targets only the player.

When a player comes within 16 blocks, it opens fire, strafing left and right and attempts to gain altitude. Ghasts flee when hit in Creative.

Ghasts require a line of sight to the player before firing. Any solid blocks (including transparent blocks) can interfere with the line of sight.

If the player is able to fly inside an aggressive ghast, it may die of shooting fireballs at itself. They are also careless about being hurt by blasts from short-range shots.

Data values
Ghasts have entity data associated with them that contain various properties of the mob.

Ghast fireball
The ghast's fireball attack has a straight trajectory unaffected by gravity and a theoretically infinite range, although it disappears after 1 minute. Fireballs do not track the player once fired, are slow, and can be deflected if the player hits them with a projectile, fishing lure or melee attack. At close range, it is one of the most powerful mob attacks in Minecraft, fourth only to the explosion of a creeper, the melee attack of an iron golem, and the explosion of a wither. A direct hit deals projectile damage from the impact, and up to, , or  explosion damage from the blast, depending on difficulty. When two ghast fireballs collide, one is deflected to a random direction while the other explodes upon impact. Blocks are also set on fire by the explosion. If a ghast is killed, fireballs launched by that ghast disappear. A fireball deals damage to a ghast if the fireball was rebounded by a player.

The minimum blast resistance required to absorb all blast force of the ghast's fireballs is 4.034 (about the equivalent of basalt which is 4.2).

When a player hits a fireball, only the projectile damage dealt by the ghast fireball counts as the player's kill.

Entity data
Ghast fireballs are also entities that have associated entity data.

Trivia

 * In English, "ghast" is an archaic word meaning "ghastly". H.P. Lovecraft first coined its use as name for monster (a vaguely humanoid one, in The Dream-Quest of Unknown Kadath), but "Ghasts" have appeared in many other fantasy stories and games. In Minecraft, it also seems to follow a pattern of playfully replacing the letter "o" by "a" (Netherrock → Netherrack, Ghost → Ghast).
 * The player can go inside of a ghast by falling through the top of it or flying up underneath it. If the player stands on top of the head, the player sees inside of it.
 * If a ghast is trapped in a 1-thick cube, it shoots fireballs through the cube. This is because all mobs that shoot spawn the projectile one block in front of it to prevent the projectile from hitting the mob.
 * On rare occasions, ghasts spawn in such a way as to see through blocks (usually trapped on all sides in a tight area). When this happens and the ghast has a "line of sight" through those blocks, it launches a fireball in the player's direction.
 * C418 revealed in an AMA on Reddit that ghast sounds are taken from his pet cat, which he makes when disturbed while sleeping.
 * Two ghasts are featured in the LEGO set "Minecraft Micro World - The Nether", along with a Zombie pigman.
 * Iron golems and vindicators named Johnny do not fight ghasts unless they are close enough, even in this case, it's rare.
 * When killed with its own fireball, the ghast turns orange rather than red. This is because the ghast is set on fire.
 * Splash potions affect ghasts only when hitting them on their lower half.
 * Despite not having visible feet, ghasts are still capable of making footstep sounds.
 * Ghasts are the only non-undead mob that withers are not hostile toward.
 * If a player hits a fireball using an item with the Looting enchantment, any mob killed by that fireball has its drops affected by the enchantment as though the mob was killed by directly using the item.