I have been trying out the game's default Atronach birthsign (before perhaps modding it to mirror how it was in Oblivion) with Hervor. I have been seeing something weird though. Sometimes when Hervor is hit by an animal, the swirly spell absorption effect goes off around her. It does not happen all the time with animals though, and never when she is hit by npcs with weapons.
Has anyone else seen this? I cannot tell if she is actually absorbing any magicka or not, since too much is going on when it happens. I am wondering if the animals are trying to give her a disease, and she is absorbing that somehow instead? I think the game treats diseases as spells, so it might.
Edit: Looks like I was right. The UESP page on Spell Absorption says it absorbs everything except base weapon damage, falling damage, and drowning damage. Wow, this birthsign is hugely overpowered!