Game Mechanic Executions? How are you going to force that? Unless this religion becomes big enough, people will simply just leave the area and go somewhere else instead of being executed.
That's if you do it poorly. In a well-crafted society, being sacrificed to the gods would be the ultimate reward for a warrior who has fought well in battle. You wouldn't kill everyone wholesale, of course. Let's not get greedy - BM isn't a big enough game for that. But let's say you have a religious war, and the heads of the religion come together beforehand and say - well, okay, the gods are displeased with us. The crops have been failing, and people are restless. To remedy this, we're going to war. In addition to that, to placate the gods, 3 nobles from each side are going to be sacrificed out of all the nobles captured in the war. The people who capture these sacrificed nobles? Honours are heaped upon them - lordships, power, gold, titles. What determines who is sacrificed? The gods, obviously. There will be signs. (Or backroom political dealings, who knows.)
In summary? Hell, just make it fun. People can leave and play in traditional realms where they idle for weeks on end until they eek out a rural lordship and then idle for weeks on end until they eek out a better one, or they can join a society where fortune is won and lost in radically different ways.
