Shieldbreaker, Sword of Force

Equipped creature gains double strike and
indestructible, and must attack or block each
combat if able.
When equipped creature blocks or is blocked by
a creature with 0 power or less it takes damage
equal to that creature's toughness instead and
loses indestructible until the end of combat.
Equip {0} (only activate this ability if
Shieldbreaker, Sword of Force is not equipped)