The first HFS contained weather demons. Weather sphere appears to have no effect on the shape of the HFS. Everyone died.
Second Embark. The world has passed into the Second Age of Myth. Second HFS showed the same contents. Engravings of submissive gestures, torture, burning, withering, dead and screaming sentients. Found Justice Demons. Justice appears to have no effect on the shape or contents of the HFS. Everyone died.
Third Embark. Miner frozen due to " leather". HFS identical to first and second. Found Charity Demons. Charity has no effect on the shape or contents of the HFS, nor does the [GOOD] tag. Everyone died.
Fourth Embark. 'You Have Arrived' screen doesn't list an animal. Instead, it lists 'ere the beasts get hungry'. One instance of " leather", no deaths. Opened HFS. Chamber is the same as usual. Sent unwitting miners inside and waited. Found Wealthy Demons. Sphere of WEALTH does nothing. Everyone died.
Current outlook. Only the spheres already associated with demons do anything.
FIRE is attached to the SoF
MUCK and WATER is attached to the frogs.
DEPRAVITY and THRALLDOM is attached to the tentacles.
FIRE, DEATH and TORTURE is attached to the leaders.
For unnassociated demons, there appears to be a generic chamber filled with generic masterful engravings of terrible things, charcoal and ashes on the ground, body parts and caged/chained/spiked/dead sentients.
Still cannot for the life of me find out why merpeople became megabeasts, my dwarves were wearing cave fish silk, and how that ' leather' got in there.