Perdition Emperor Dragon, Dragonic Overlord the Great

:[Legion 20000]"Perdition Dragon, Dragonic Neoflame"(If your opponent's vanguard is grade 3 or greater, this unit may return four cards from your drop zone into your deck once, search your deck for the specified card, and Legion) :[ 1 & Choose two cards from your hand, and discard them] At the end of the battle that this unit attacked a rear-guard, if this unit is [Legion], you may pay the cost. If you do, all of your vanguards. This ability cannot be used for the rest of that turn. (Even if you do not pay the cost, this ability cannot be used for the rest of that turn) :[Choose one of your rear-guards with the same card name as a unit on your , and retire it] When this unit's attack hits, you may pay the cost. If you do, choose one of your opponent's rear-guards, and retire it.