Here's my idea:
Bathed in Light
Increases the priest's mana regen from spirit by an additional 20% while in Serenity or Sanctuary chakras. (making it 60% of spirit)
edit: just thought of another thing that could be added. Make the effect disappear when changing chakras for a short amount of time. Could add in some more choices. Do i change chakras now, or will i need the extra mana?