How come my opponent has creatures that automatically heal after battle?

[Demonic God]

I'm hitting this idling guy, and killing his ritual. Why do I still seeing the same creatures in the next battle? How come he doesn't have to heal them back?

[Dracoloth]

The regeneration stat allows creatures to heal after a battle is over. Some creatures have this stat on their own, but it can also be given to creatures by the player by selecting a higher vitality on the ritual's slider.