Ghast Farm (Gunpowder + Ghast Tears)

Ghasts spawn in open 3D space rather than on a floor, and they favor Soul Sand Valley specifically, at a rate high enough that every real ghast farm is built there and nowhere else in the Nether.

Because ghasts need a big open volume to spawn into, the enclosure has to be genuinely large: a hollow box of solid blocks so nothing else can spawn competing for the space, with enough internal room for the spawn algorithm to actually place one. Slabs or carpet on the floor keep zombified piglins and other Nether mobs from stealing the slot.

Ghasts float and shoot fireballs instead of walking, so funneling them works differently than a ground-mob farm. Water pushes a floating ghast the way it'd push a dropped item, since ghasts don't pathfind around water the way land mobs do, which is how most builds herd them toward a kill point, whether that's a lava blade, a fall, or a manual finish.

This is one of the more dangerous farms to build, not run. Fireballs hit hard and knock you around, and you'll be spending real time exposed in open air while you construct the enclosure. Bring Fire Resistance, and seal the walls before you let spawns start rather than building in the open with live ghasts around.

Ghast tears are really the whole reason to bother with this over a simpler gunpowder source. They're needed for Regeneration potions, and short of trading, this farm is the only reliable way to get them at all.