This Ruler can J-activate into Diabolos, the Nether Tyrant .
Sariel, the Lord of the End
Sariel, the Lord of the End
Attribute: Darkness D
Card Type: Ruler
Race: Fallen Angel
Abilities: [J-Activate] Pay Void 5 , discard three cards in your hand.

[Activate] Pay Void 4 : Put a resonator in your graveyard into your field.
It can attack this turn. At the end of turn, remove it from the game, if it's in a field or a graveyard.

Sets and Rarity:
[Valhalla Cluster] The Dawn of Valhalla [EN]

[Valhalla Cluster] The War of Valhalla [JP]
(2-108 — Rare)