The Imp is a better choice, but there are merits to the Intellect Devourer as well...
The real change that I would most like to see is to have the familiar be permanently there once summoned.
Us' higher hp is about the only merit I can think of. It would be a better damage soak than the imp. But given all the other advantages the imp brings to the table, I don't see how Us can even compare.
What do you mean by permanently summoned? The Imp pretty much is unless you long rest, or it gets killed in combat. I like being able to resummon it because anytime it takes any damage I can just resummon a fresh one and it's back to full hp.
What would be the benefit to being permanently summoned?
