[Thar] Dark Seal (written)

[Thar]

Dark Seal (SPELL)

Continuous

While this card remains active: Players cannot activate the effects of cards in the graveyard or sent to the graveyard.

[Flash Flyer - Sakura]

Considering how much Decks love the Graveyard and triggering, this is pretty much a floodgate. Sure, you can MST or bounce this card, but let's assume the opponent doesn't have removal on them.

 

Or really, this is the Spell version of Soul Drain (or whichever one of the "Drain" Traps that negates stuff in the Graveyard), which is Limited, last time I checked.

 

Pendulums probably don't care, but a lot of common Decks do.

 

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I would add some form of internal destruction (meaning that if something happens, then card self-destructs), similar to what Vanity's has for locking off SSing.