Once per turn, if a face-up "Yubel" monster(s) you control leaves the field by card effect: You can add to your hand 1 "Yubel" monster from your Deck, GY, or banishment, whose original Level is 1 higher or lower than 1 of those monsters, then you can Special Summon it, ignoring its Summoning conditions.

You can only activate 1 "Nightmare Throne" per turn.