If I use 2 Cleaves (each giving a unit ASSAULT 3) on the same unit, does it get +3 or +6 (does ASSAULT stack)?

Ruling: ASSAULT is a stacking keyword. Multiple instances of ASSAULT add up together, so two Cleaves giving ASSAULT 3 each would result in ASSAULT 6.

Nuances:

• ASSAULT only applies while the unit is an attacker
• ASSAULT is functionally "While I am an attacker, I have +X [S]"
• Once combat resolves, the unit is no longer an attacker and loses the ASSAULT bonus