Ghast flying above lava in the nether. Ghasts are huge, floating Nether mobs that shoot explosive fireballs at the player.
To spawn naturally, ghasts require a solid block below them and 5×4×5 free space in order to spawn, and only spawn in the Nether, in any light level.
Ghasts drop 0-2 gunpowder and sometimes a ghast tear. They also drop 5 experience when killed by a player.