It's a tadpole in your brain, living sentient creature, not a power granted to you by being the child of a god nor a pact with some powerful or all powerful being or some shard/item of power. It's a creature, that yes just maybe you can control, however, you would also retain a constant fear that the creature will break free of your control and consume you. It's more having a slave rather than having power and that power would never truly be yours, it's the slaves. Having your own power is great, relying on someone else for power is a weakness. Once again you are also aware, if you investigate, that the Absolute are a bunch of Mind Flayers, and the Absolute look like some kind of mass sleeper invasion. There is a slight possibility that this is a smoke screen, but it's doubtful. Members of the cult aren't aware that they have a tadpole in their head and when told this, Priestess Gut as the example, they reject it with hostility. Genuinely there is no rational for dealing with mind slaves. Hell even going in killing Halsin and retrieving his journal makes more sense than the mass slaughter of the grove as its one of the fastest routes to figuring out what to do about the tadpole. You're never given a sound or rational argument for going with the cultist, you can most certainly head canon something but that only works while we are sitting in the Act 1 camp. Act 2 and 3 may drive it further home that siding with them is not a sane or rational choice. You get little out of the tadpole anyways, you can see into other tadpole crew minds, be a dom and you can intimidate a bunch of goblins cause of a shiny brand, its a hive mind device and for me that's a hard pass.
