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Jokes aside, I think it's a card you'll want to include in your Subterror Deck to give you options

Alternatives include the filter lands, the SOM fast lands or even pain lands

Vyon is used to send Shadow Mist, or a destiny hero to the graveyard, then allows you to banish one hero from your graveyard to add Polymerization to your hand

While it offers the ability to revive a FIRE monster from the graveyard and provides a way to recycle banished FIRE monsters for a draw, there are potentially better cards like Monster Reborn for monster revival or Pot of Avarice for mass monster recycling and draw power

Agent of the Shadow Thieves plays quite well alongside blacks many ways to pay life for beneficial effect, making your commander(s) quite potent attackers against whoever is unfortunate enough to have the most life