Strength Sap

Lowers the target’s Attack by one stage. Heals the user by the target’s current Attack, including modifiers, but not including this move’s Attack-lowering effect. If the target’s Attack is already at -6, this move will fail. In any other situation that would prevent a stat modification, the healing will still succeed.

“The user restores its own HP by the same amount as the target's Attack stat. It then lowers the target's Attack stat.”