Minecraft wiki entry for Development_versions, associated text: Generates in the Deep Dark biome.
Emits soul particles after a mob dies within 8 blocks, and grows sculk related blocks.
Spreads sculk blocks to wherever a nearby mob dies. The amount it spreads depends on the amount of experience the mob is meant to drop.
Even if the mob doesn't drop experience as it wasn't killed by a player, the blocks would still spread based on the amount of experience it normally drops.
The experience will not be dropped in these cases.
The charge decays over time, faster the furthest away from the catalyst it moves.
If a charge decays more than 4 blocks away from the catalyst, it has a chance of creating either a sculk sensor (90%) or a sculk shrieker (10%).
If a charge decays more than 24 blocks away from the catalyst, it merely vanishes.
Drops only experience when broken without Silk Touch.
Emits a light level of 6.
Blooms when activated.
Can only spread sculk on blocks in the sculk_replaceable tag.