Astaroth's Reckoning

Cocytus (Cocytus cards may only be put into decks through effects from Prince of Cocytus. If your library
were to be replaced, put all Cocytus cards back into the Cocytus Deck.)
This spell may only ever be played during main
phases on your turn.
This spell cannot be countered.
Target player's life total becomes 1. Until the beginning of your next turn, that player's life
total cannot change.