All living creatures have morale, their will to fight. The GM calls when to make a morale check. Morale checks always have a DC 11. Success means they stand and fight. Failure means they surrender or flee. PCs rarely have to check morale.

Like any check, roll a D20 against one of the following:

• For PCs and NPCs, roll a WIS check adding proficiency bonus if it is appropriate
• For Monsters, roll against their morale score

These checks should have advantages or disadvantage based on the circumstances as outlined in the combat rules.

The GM can call for one or more morale checks; generally when: • the battle begins • after the first combatant is killed • when the leader or expert is killed • when the tide of the battle is obvious.

PCs and their retainers always roll morale individually. The GM decides if monsters roll as a side, a group based on type, or individually.

copied from 5TD

I have some morale rules in the Combat Chapter, basically follow this outline with some more detail, and some modification/clarification on when to check.