This is about what should be the role of the OTHER half of the Outsiders. We've got the Tanar'ri, the oft ignored Yugoloths, and the Baatezu. However, what is the adventuring potential of Celestials? How do you roleplay the Outer Planar embodiments of Lawful, Neutral, and Chaotic Goodness?
What kind of conflicts can they provide?
The first thing about Celestials is to remember they don't come from Heaven. Everyone forgets that.
In Planescape they come from Ysgard, the plane of glory and kinship with your warrior bands or Bitopia with its clever games of wit, trades and crafts. All the Upper Planes are different and more importantly they are filled with the souls of good people, Celestials aren't naive in the ways of mortals even before they leave their home.
Conflict comes from several points.
Does a Celestial have the right to tell others who is right and who is wrong? Over the eons angels have fell, can a devil rise? Should evil be slayed or taught to be good, is it more Good to try and convert evil to good reguardless of the cost to yourself?
Many Celestials are under the banner of a God, are they truely good or did they just get the best spot on Mount Celestia all those millienia ago? If their god makes a mistake, are they worth following? What if your god dies?
Long ago the Pact Primeval was formed, the Devils now torture sinful souls... What if your god sent a hated foe to the Nine Hells and his sin is no longer considered such (perhaps he stole the gods lover from him), do you free him against the gods wishes?
A Celestial's constant struggle is this, Evil can imploy any tactic it needs to win. Celestials must remain holy.
As for how to roleplay them, just roleplay someone who wants to amount to the kind of person others think they are. Good guys. :mrgreen: