Sheoldred

Menace
When Sheoldred enters the battlefield, each opponent sacrifices a nontoken creature or planeswalker.
4B: Exile Sheoldred, then return it to the battlefield transformed under its owner's control. Activate only as a sorcery and only if an opponent as eight or more cards in their graveyard.
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The True Scriptures
(As this Saga enters and after your draw step, add a lore counter.)
[I] For each opponent, destroy up to one target creature or planeswalker that player controls.
[II] Each opponent discards three cards, then mills three cards.
[III] Put all creature cards from all graveyards onto the battlefield under your control. Exile The True Scriptures, then return it to the battlefield (front face up).