The Undying Legion (Collector's Rare)

2 Level 7 monsters Once per turn, you can also Xyz Summon "The Undying Legion" by using 1 Rank 6 Zombie Xyz Monster you control (transfer its materials). During your opponent's Main Phase (Quick Effect): You can detach 2 materials from this card (or just 1 material if all this card's materials are Xyz Monsters), then target 1 Attack Position monster your opponent controls or 1 monster in their GY; attach it to this card. You can only use this effect of "The Undying Legion" once per turn.