Black & WhiteEdit
In the first game, a god can sacrifice living beings as soon as he/she builds a worship site. This building comes with an altar shaped like a pyre where the gods can literally drop any plant, animal or villager inside. These are converted into prayer power based on the lifeform itself.
Plants yield the least amount of prayer power while villagers (particularly young ones) yield the highest amounts.
Curiously, it is possible to gain prayer power from dead villagers (their skeletal remains). I do not know if this is considered evil. It is also possible to drop living beings on other gods' altars, provided there is enough influence to reach them.
Black & White 2Edit
They can be used as a source of Evil alignment, though if done too often, the population will be scared of the player for a while.