Spawner Core

Spawner Cores/$ are the beating heart of vanilla Spawners/$, which contain the essence of the mob to be spawned. They can be forcibly extracted from a Spawner with a Spawner Extractor/$, but it's also possible to make these, and use them in the more powerful Pressurized Spawner/$. Note that it's possible for a Spawner Core filled by a Vacuum Trap/$ to contain the essence of several different mobs, which may or may not be desirable. You can release a random mob from the core by right-clicking/$ it, but this can be a bit of a hit and miss affair. Producing a core with 100% purity via Vacuum Trap/$ isn't trivial, and takes some care.