13 ways to use… angels

1) One to the classic questions is why, if there are angels, don’t they handle all the problems. I would suggest that, as most beings are a combination of good and evil, they have trouble distinguishing. Either that, or higher access to the mortal plane by celestials makes access for fiends easier.
2) Trouble distinguishing between shades of grey will also explain why celestial being living on the mortal plane prefer to live in the middle of nowhere. Virually all being have too much evil in them for comfort.
3) Angels are too proud, and too honest, to use invisibility to fight. Instead, they’ll use it to give the impression that they’re all knowing. Too use this, have the players be talking among themselves, and suddenly they realize that the angel was behind them, and they have no idea how he got there. (Deva’s will use change shape to achieve the same effect.)
4) Use an angel’s healing touch to provide small, min-quest rewards. If you want to annoy your players, have the angel decide who to heal based not on need, but on virtue [how pious they are.]

Deva

5) The deva will use its shapechanging ability to test whether they deserve to be helped. If you want to make it challenging, provide reasons for them not to help. (Example: An old lady needs help crossing a bridge, but they’re late for an appointment.)
6) The deva likes to give advice in the guise of kind old elderly people. This can lead to interesting circumstances, when such a person who is not the deva say something to the players. This can be either coincidence, or a villain taking advantage of it.
7) When evil [fallen], the deva will use its shape change ability to lead them into terrain that favors the deva. For example, a narrow path where they’ll have trouble using their numbers, with ample foliage to mess up ranged.