When your opponent Normal or Special Summons a monster(s): Target 1 of those monsters and 1 Spellcaster-Type monster you control; send both monsters to the Graveyard, then you can Special Summon 1 DARK Spellcaster-Type monster from your Deck or Graveyard.
How to Get
Sends from your field to your Graveyard / Sends from your opponent's field to your opponent's Graveyard
Special Summons from your Deck / Special Summons from your Graveyard
This could be a super rare for the Arkana event. It's OP I this current card pool, but I would argue it's not as OP as negate attack from the Mokuba event (which, by the way, unless you negate its activation, forces you to immediately end your turn with only one main phase)