Harmony - Troop Symmetry

I'm thinking about how to enhance the guardian angel, as it will be a powerful ability for the Haven faction. The question is, what bonuses and in what quantity can I add to the guardian angel? It would make sense to give army-wide bonuses such as defense or magic resistance (like magic depletion). Or perhaps some other way. I haven't created any skills yet, and I know that you can add a rune (as done in the related thread), but I can't find a suitable rune. Any ideas?