Casting Darkness over summons (bearing the effect of Ultravision) causes the summons to aggro the caster - even if the caster is the summoner.
I've noted that this usually only happens when the summons are in the AoE when the effect is initially thrown down; when throwing Darkness first and sending them into it, this does not seem to occur.
The summons also do not turn red, they remain blue.
It is because darkness is a hostile AOE spell and if you hit them and they don't have aggro on something else they will attack you sometimes.
This is somewhat recent. Normally they would just turn into awkward pacing creatures going between the target / darkness / summoner. It's odd that they attack the summoner.
I can confirm this as an old issue.
Mriri used to have her own shadow punching her face when she called for her dark mantle.
Familiars and animal companions are known for doing the same thing, statistically I see it the most from panthers out of my nwn experiences.
Ahh, yes. I do remember that happening with companions under Ultravision. But they never attacked their respective character, when it was they who cast the darkness, the way I recall it.