Basically, what I want is several effects which balance things out for the weak caster who summons "the grey":
1. There should be a degenerative effect as things break down slowly, no more than a few hp dmg per round, etc.
2. It should be harder to will yourself to move, especially quickly or violently.
A lot of that is roleplaying and storytelling, but I want it to be balanced. This is totally an NPC class using it, but the principles need to be sound, for me. Does this make any sense? If not I'll edit the post with a better explanation...