Kinda my concept of them, yeah! Only instead of "to fuel their power," I imagine it being "for the lulz." They're like the wings of some wicked butterfly, causing hurricanes of despair and moral collapse half a world away, because they love a miserable world.
This brings them into conflict with PC's, who might see that all the problems they've been fixing seem, when they connect the dots, to relate to something much more destructive in total than any individual act. A demon will torture you. A devil will persuade you to do the torturing. A yugoloth might cause the breakup of the marriage of the parents of the general who, never being shown empathy in the care of the corrupt orphanage in the city, is unable to feel compassion for his prisoners, and so orders the torture of hundreds. You can be sure when you slay a yugoloth that you're doing the world a favor, but it's not usually easy to draw clear lines of cause and effect.
A'kin, as he is described in a lot of the Planescape products, is the
perfect example of this. What's so bad about a friendly acanoloth selling you magical geewgaws? Man,
who knows? Possibly everything? Possibly nothing? And is that rivalry with Shemeska a charade, or are they working together? It's a load of questions with no answer. This is the emotional state of a player up against a yugoloth: like every action is built on
nothing.
What's wrong with a man in a black suit hanging out in the diner near where you saw those strange lights? Why should you object when he offers to buy you a slice of rhubarb pie? Why does no one else who was there seem to remember him? It's pure
Paranoia Fuel.