Desolate Wastes: Rules (Morale)

Since I want retreat to be an option for my monsters and NPCs, who might not want to fight to the death, here is a standard based on some rules of thumb for when a unit should retreat or rout.

Check Morale when:

If they lose half their number.
If their leader is killed in a bloody or disgraceful way.
If escape would be easy and more beneficial for their mission.

Opposing factors, those that would have even a coward stay to fight, would be:
Risk of torture or imprisonment.
Their leader inspires them to fight on.
Their leader's death was inspiring and tragic.
The players are clearly going to kill everyone behind them, so they need to stay and protect them.

Roll d20+level or CR of monster plus any opposing factors, on a 10+ morale is good and they continue with their plan, less then 10 they look for escape or surrender (if possible). Use individual checks where feasible.