Voadam
Legend
Cthulhu mythos cultists worshipping mythos entities that ultimately are hostile to human life are a trope and a staple.I could get behind that, because I think that we have long noticed the issue with Evil Extraplanar entities and gods that they just don't make much sense to worship. As presented, no one in their right mind worships Tharizdun, because he wants to destroy everything and leave nothing but an empty void.
Often big mythos entities are considered gods, though you could conceive of them as not-gods depending on the paradigm/definition used.
Most of the worshipers are considered not in their right minds, but the evil cult is generally a standard.