Silverfish Spawner XP Farm

This is the one spawner farm on this list tied to a structure you're actually trying to protect rather than freely rebuild around. Strongholds hold the fixed End portal frame you need to reach the End, and a silverfish spawner is often found right in or near that same portal room, so the build has to work carefully around the portal instead of walling it off by accident.

Silverfish have a defensive trick worth designing around directly. They can hide inside normal-looking stone blocks, indistinguishable until you break one and a silverfish bursts out, and using regular stone anywhere in the containment structure risks stray silverfish seeding more infested blocks over time. Most designs stick to glass, wool, or anything silverfish can't infest for the entire room and funnel.

The funneling itself is the familiar water-and-signs pattern from other spawner farms, sweeping silverfish toward a kill point. They're low health and deal only minor damage individually, so the kill mechanic can stay simple, often just a short drop and a single hit, without the heavier safety margin a blaze or witch farm needs.

A sword enchanted with Bane of Arthropods helps a lot here, since it applies bonus damage against the arthropod category, which covers silverfish along with spiders and cave spiders. Manual kills go noticeably faster with one equipped.

Since this sits right next to your route into the End, most people only build it if a spawner happens to be conveniently placed in a stronghold they're already exploring for the portal. It's a decent bonus, not something worth searching multiple strongholds to find.