The text of Warrior Priests reads "The first point of damage assigned to this unit each turn is redirected to one target unit in any battlefield." What is the definition of "assigned?" Is it any damage dealt to the unit, damage assigned during combat or any damage that specifically targets the unit?

deashira said:

Assign damage is when you take damage token from the pool and place them NEXT to the target(s), ready to be applied in the Apply Damage Step. All damage is first assigned and then applied.

The timing works like this -

1. damage is pooled (regardless if it is from effect or combat)
2. damage is assigned (all damage is considered assigned simultaneously even though it is obviously placed one counter at a time)
3. the Forced Effect kicks in making one damage assigned to Warrior Priest assigned to another unit following their ability restriction
4. if it is combat damage then there is a Player Action Window that follows (if it is non-combat damage you skip this sub-step)
5. damage is applied (as damage is moved on to the units any damage canceling effects move the relevant number of damage counters back to the general pool rather than on the unit or zone).