I was getting extremely low fps rates in the Erebus and noticed the entity count was absurdly high. Looking around found this... There is something a bit broken with the wisps with Erebus installed.

It looks like the config for max wisps per chunk is ignored and they just never stop spawning. Thanks.

Versions:
Forge 14.23.5.2808
EerieEntities-1.12.2-1.0.6
Erebus-1.0.25

Thanks for the issue report. The max X per chunk config options are a bit misleading. The way Mojang's spawning system is setup, max per chunk actually means max that can spawn per chunk, in a single spawn tick. The will-o-wisp is an ambient mob, like the the bat. I am guessing the Erabus doesn't have any ambient mobs, meaning the will-o-wisp is able to fill up the entire cap right. I will look into a proper fix for this, but for now I think the best solution would be to just remove the ability for this mob to spawn all together.