Must Vent about Breath of Winter

[tinkthank]

I just played a turn in which my superior force attacked an independent province and routed the enemies fairly quickly. These, however, were somewhat slow, and thus on the battlefield for about 3 rounds before the battle ended with the stragglers leaving the field.
On the first of these rounds one of my mages cast Breath of Winter, even though *NO* enemy units (which were routed anyhow) were even close. He thereby killed my prophet, who happened to be standing nearby, on the Last round before the battle ended.
Otherwise, none of my units were killed at all.
On a crowded battlefield, it will be hard to place all of my mages away from each other and their bodyguards so that they dont kill each other, but I would greatly appreciate not having to do so.
Please, stop the madness. Mages Against Drunk Casting.