I have always used the purple treachery on a second Dark Charm and poison spiked pits. If I can, I will try to get the animate weapons in there as well. Dance of the monkey Gods and rolling stone are too high priced in treachery and too situational to really make them useful when you need them.

Antistone said:

Hm. Actually, I may be wrong about this, though I would maintain that an extra card in your starting hand (even for 2 treachery) is genuinely a better deal than more than half of the purple treachery cards. Early on in the game is when most of the overlord's cards are most useful, so being able to hit the ground running, as it were, is good. But poison pits are admittedly pretty good too.

dark charm, animate weapons or dark relics are bad? wow..