Guardian Farm (Ocean Monument)

Ocean monuments naturally spawn guardians (plus three elder guardians, one per monument), and the whole idea of a guardian farm is turning that ambient spawning into a controlled, mostly-drained chamber where every spawn funnels to one kill point instead of guardians roaming the whole structure.

Deal with the three elder guardians first. They inflict Mining Fatigue on anyone nearby, which makes building anything in range genuinely painful. Milk cures the effect temporarily if you'd rather fight through it early, or you can build the initial structure from outside the affected radius and push in from there.

Fully drained builds use sponges (which, awkwardly, only come from killing elder guardians in the first place) to soak up the monument's interior water, letting guardians still spawn there since they need water source blocks specifically. A well-planned drain leaves isolated single-block pockets exactly where you want spawns to land, funneling straight to a fall shaft or kill area.

The no-drain alternative skips sponges almost entirely. Build a spawning platform above the monument at the right depth, let guardians spawn naturally, and let them fall or swim into a nearby kill chamber. Much faster to build since there's no lengthy draining process, at some cost to spawn rate.

This is one of the higher-value mob farms for late-game prep. Prismarine feeds sea lanterns and armor, raw fish feed a smoker for fast passive food, and the XP from a well-built farm rivals or beats most spawner farms without needing a rare natural spawner to be found first.