Ultimate SpellBuffCost: 6
Your units get +3 ATK / +3 armor this turn. Excess combat damage they would deal to units and heroes hits that opponent's base. (This takes precedence over overpower.)
Nature stops for no man.
GreenGrowth Ultimate Magic

Card-Specific Rulings
Units that have overpower do not LOSE overpower from this spell, so a Wandering Mimic would still see those units as having the keyword. It's just that Stampedes instructions for where to send the excess damage happen, and overpower's instructions don't. — Sirlin