A Rank 8 for Rank 4s (most of the time)

[Dragulas]

 

[spoiler=Lore]2 Level 8 DARK monsters
You can also Xyz Summon this card by using 2 Xyz Monsters whose total Ranks equal 8 as the Xyz Materials. At the start of the Damage Step, if this card battles an opponent's Special Summoned monster: You can attach that monster to this card as a face-up Xyz Material. You can detach 2 Xyz Materials from this card, then target 1 card in your Graveyard; add it to your hand, also skip your next Draw Phase. You can only use 1 "Void Warrior Archfiend" effect per turn, and only once that turn.

 

[The Highlander]

Interesting, turning used xyzs into a better catastor, which also turns draw phases into instant regeneration.

All in all an interesting idea.