[Twan]

Actually the only use I ever made of a slave collar was to render useless a mage mercenary when the contract was about to end.

I'd rather like a mindless effect instead of the current one (of course would be very good for already feebleminded tartarians, but for this use you usually would need to spend the 20 nature of a GoR on a magic-less tartarians, so it's not overpowered I think).