Mercer Frey is the worst thief and worst "follower" ever, but his behavior on the Speaking With Silence quest reminded me to ask about area effects. My preferred tactic when in tombs is to lure the undead out one at a time, then pick them off from a distance. Frey, however, immediately ran in, screaming, and draws out six or so Deathlords at a time. So I switched to casting Flame Cloak and then rushing in with Dawnbreaker.
But occasionally I got a message "Mercer Frey resisted flames". And when Dawnbreaker does its undead burst effect, sometimes Frey would be damaged. I thought:
- Dawnbreaker's burst effect is only supposed to affect undead, and
- the Cloak spells aren't supposed to harm allies. I've seen it happen every once in a while before, such as when vampires attack the streets of Whiterun. Every once in a while, I get "Whiterun Guard resisted flames".
So, is this a known bug? Or do Flame Cloak, Dawnbreaker, and other area effects work differently than I thought? I'm afraid to try Mayhem while travelling with a follower, now...
Edit: I should clarify that followers are definitely getting damaged by both effects, but inconsistently. Tskcool's comment about "X resisted flames" probably explains that message, but I also get followers saying "Watch it!" and "I'm on your side!", plus their damage bar visibly changes. The latter might be due to coincidental attacks from monsters, but the warning dialogue means friendlies are being harmed by effects that, according to both Elder Scrolls wikis, aren't supposed to affect them at all.
I did learn through more wiki research that elemental Cloak spells do damage neutral NPCs like guards, which is something I've seen personally. That may explain some of the messages, and might even explain Mercer Frey and now Anska, since they aren't normal followers. But I recall getting the same results with Lydia and Rayna, maybe even Mjoll. And again, it wasn'ty consistent: sometimes they are injured, sometimes they aren't.