Not using the Rage Box?

[Marlowe]

Frankly, I don't think that most of the rage spirits scaled all that well, with one exception. By the middle game, and certainly the late game, they were generally not that useful (and I got all the spirits to at least level 20). The one exception was the Reaper and the Soul Draining ability (and, to a lesse extent, Rage Draining). Reducing stacks of dragons and ogres by a third every couple of turns is pretty nice, and the only rage skill I found really useful in the late game.