I don't know if this has been brought up. If I have read the rules correctly, the folowing is true:

6 zerglings atacks a lone dark arcon. The dark arcon gets killed, but mind controls a zergling. Both sides have units in the area. The zerglings has to retreat.

Is that right? Have i missed something?

That's how I understand it too. If for example the zerg player has a splash damage somehow, then the mind-controlled zergling has to be chosen.

Yeah that is one of the most powerful aspects of mind control.

If you have maelstrom and mind control it is VERY difficult to take a space with a dark archon in it.

mathulus said:

Yes, you have. Mind-controlled units still can be destroyed by Splash Damage in the same battle.