This event sounds with the potential of having a duel tournament.
Seems that Infernal Demons keep at that harsh rivalry with humans, love it :)
Even if this is Domination specific holiday, this sounds like an idea for a battleground or pvp area perhaps? (Even tho it might not be a topic for it ill type a few words)
If both factions are that close to one another its a nice fit.
If battleground one side can launch an assault while the other defends (domination is stealing humans while sacred order is defending), and then the sides turn (sacred order launches counter attack and tries to rescue more human prisoners than the domination kidnapped).
Winner becomes one who had more villagers kidnapped/rescued.
What do you think?