if they sacrificed any of their virgins during a battle they become a possible target. I've tested with it thoroughly, and saw them attacking bogus' comrades and the like as well.
my blood mages that did nothing with virgins never got attacked.
they are unique, so they keep whatever, just like other unique folks.
So in theory you could use them as cursed item vectors by letting them eat some cheap bloodmages? Ugly surprise for whatever is strong enough to kill them.
Now that would be intresting.....Get them to equip slave collars (by having them kill a cheap blood mage with one) and anyone who kills them gets an unpleasent suprise
If I remember properly, there are three Kindly Ones, and each one attacks different commanders -- one attacks blood mages, the other two I don't remember.