Reminds me of a spell one wizard was excessively fond of... Enemies Abound, I think it was. Illusion, had a rider something like 'enemies count as allies for purposes of flanking?'Divisive Deception - level 26 Bluff skill power
You turn enemies against each other to the degree they ignore you and your allies.
...y'know, I can just look it up: "Targets Enemies in Burst....you and your allies can treat the target as an ally for the purposes of flanking until the end of your next turn." ...of course, that's just a Level 7 Encounter.