Imperial Mortar Support

This card cannot attack, but it can defend.
{3}, {t}: This card deals 3 damage to any target. If
a target survives, tap it until end of turn.
If you control three or more Imperial Mortar
Support, the above ability changes to "{3}, tap
three or more copies of this card: Deal 3 damage
to each card on the opponent's field. If any cards survive, they are tapped until end of turn."