The other, far more dangerous creature dwelling in the deeps of the
Nether, is the Ghast. These vicious flying jellyfish are enormous
(4x4x4 bricks large) and shoot exploding fireballs from their giant
mouths if they catch sight of you traversing their realm.
In addition to being quite deadly on their own, they also enjoy the
distinction of being completely immune to light sources when
determining spawn points. Meaning that placing a few torches in your
Nether Castle won't protect you, and there is nothing more frightening
than having a ghast spawn in your bedroom. To overcome this, make sure
you do not build larger than 4x4x4 in any single room, and get creative
with your corners or furnishings â€“ ghasts require a 5x5x5 open area in
which to spawn.