Hey there, just thought I would share what I found.
During the quest "Betrayal" you get teleported up on the top of a fortress, you have to turn a guy's monsters (Blightblood troll) against him. (your disguise will wear off and everything will turn evil to you when the event starts,) however when I started the event the 2nd time the event did not begin, I did not lose my disguise until I debuffed it myself. I then used my item to take control over a mob, to the left of these elite mobs are small packs of minor ones.
The thing I did was to tag the lesser mobs, then killing them off with the elite monster.
Here are some screenies to clarify it all:
1: The debuff not wearing off, mobs stay friendly to you until you debuff it. Under normal circumstances this "buff" will wear off as soon as the event begins.
2: This is the spot where the lesser mobs can be found (instant respawn), just tag them and guide your Blightblood Troll to kill them (hits for 2-5k) and has got a decent amount of hp. Also this troll has got an ability to heal you.
3: As you can see on this image the Blightblood Troll gets the killing blow, but I still get XP for it.
I failed horribly at this, I wasn't really prepared, but maybe you will find better use of it.
by Simey