Minecraft wiki entry for Sculk_Catalyst, associated text: The means of death of the mob is irrelevant; mobs can die from being killed by a player or tamed wolf, which yields experience, or by any other means, which does not yield experience; any kill is accepted by the catalyst. In addition, baby animals, which also do not yield experience when killed, also contribute to the catalyst. Rather than granting experience, a bubbling charge spawns where the mob died, and it travels through sculk until it finds a replaceable block. The strength of the sculk spreading depends on amount of experience the mob have dropped when it was killed by a player or wolf. Several sculk charges may end up on the same block and merge, up to 1000 experience per block.