Eradicator, Vowing Sword Dragon

(This ability is active if you have four or more damage):When a Narukami rides this unit, choose one of your opponent's rear-guards in the front row, retire it, and choose your vanguard, and that unit gets +10000 until end of turn.:When this unit attacks, if the number of cards in your opponent's damage zone is three or more, this unit gets +2000 until end of that battle.:Lord (If you have a unit without a same clan as this unit, this unit cannot attack)