Art cards cant be used in gameplay, however
But, when it comes to assessing the value of these cards, it's not always about their power or which card sees the most use in player decks
Getting an artifact synergy is very strong with combos and synergies
These decks tend to focus so much on their combo versus you that if you can spend one mana and one card preventing them from doing that, your other cards will be more than enough to win the game
Command provides redundancy with Dragon Fodder and plays nicely with both aggro and control strategies
Double-faced cards show transformations or key moments, like Kefka, Court Mage/Kefka, Ruler of Ruin, Sephiroth, Fabled SOLDIER/Sephiroth, One-Winged Angel, or Clive, Ifrits Dominant/Ifrit, Warden of Inferno