You take it to them solo outside the village or the pit, and you probably die, but you still try.

Thinking back, there were two mummies, I think two super conjies and a lich in my time. Tzar was annoying because he ran around in a horde with an orc, giant and bard (instant death) and the scarab mummy really didn't bother me all that much. The lich I don't recall ever fighting. If I think in terms of toughness:
Scarab mummy
Anath mummy
Conjie 1 that was chancellor
Nabigah
Then probably the lich.

I'd throw down against all of them solo though, but I know killing any of them would be a long shot and death pretty much a given.
I'd probably allow ganging of the mummies (if they had armies) and the lich since I think it was a scion.
Conjurers, not ever, even though both of them tore through the village pretty easily.