Stacking Effects-- How do they work?

[the_ideal]

I was wondering several things about stacking:
What determines if two things stack? Can two devotion auras be made to stack with each other? What happens if there is a unit that is within range of a devotion aura that gives +3 and a devotion aura that gives +5?

Thanks!

 

[Faust]

Auras only stack if you give them different buffs.
The two devotion auras with the same buff, as you said, only give 5 armor.
If you were to add a different buff to either one, it will be 8.