Quote Originally Posted by Eldan View Post
The one ability of Arcanaloths that has always intrigued me the most was one that I only read about once, and it must have been a pretty off-hand mention, because not only haven't I been able to find it again, it's also basically never used anywhere:

They can cheat themselves into callings. When a mortal calls up some other fiend, or even some non-fiend creatures, a prepared Arcanaloth can intercept the calling and insert themselves. That, plus a disguise, means that a mortal thinks they might be calling up a spirit of knowledge for information, but might instead get an Arcanaloth who will then cruelly manipulate them.

Now, doing that to a PC is a bit dickish and I wouldn't do it. "Haha, you thought you called an angel to help you fight the evil lich, but instead, you got an arcanaloth who is backstabbing you in the boss fight!". Nah. But if that happened to an NPC? Great plot hook! A well-meaning seer is calling up an oracle spirit, or the underground freedom fighters are summoning eladrin to help them, but instead, they get a fiend who is manipulating them to Hades' ends.
Pretty sure there was a devil that could do that in 3.5.

It is a good niche for fiends though, fits better than the kill/maim/burn/repeat a lot default to.