I also think that unless Ob Nixilis proves playable in Pioneer or Modern, you might want to trade off any ones you arent actively playing with sooner rather than later
Everything that can be sacrificed is going in the graveyard, every removal spell is aiming in the wrong direction
Other grixis cards such as Don Andres, the Renegade, can also turn creatures into pirates while doubling your Treasure generation
In Limited, I can see it being a nice pick in draft
For example, In addition to these archetype-specific cards, each two-color pair has multiple signpost uncommons
By drafting multiple copies of Altanak, the Thrice-Called and Say Its Name, you can build a unique graveyard deck with a payoff unlike any other