Circe was a minor Greek Godess of magic. A Witch, Enchantress, or Nymph. Using magical potions or a Wand she would would transform her enemies into animals.
The Cup of Circe -- a Woe that would transform all units of a faction. Two options for this:
1) All current units for a faction would be converted into either Pigs, Sheep, or Horses. This would nominally adjust the resource counter up by 1 per unit transformed into the relevant farmyard animal. Obviously the main effect of this is the removal of the units from the board, the addition to the animal resources is pretty much just for the theme.
2) Something more powerful. Any unit on the current faction is transformed into a random mythological. Or even just other unit.
1) is a bit of a tamer an effect. 2) is a bit more of a profound effect although not as thematically accurate as Circe generally transformed people into farmyard animals, usually pigs.
Feel free to offer suggestions to improve the name or the mechanics of this idea.