The last card is an art card, which is not a game piece but includes blown-up versions of card art
The Pack 4 Deck Commander Marvel Super Heroes brings together in a single set the 4 Commander decks from the collaboration between Magic The Gathering and the Marvel universe
When mulliganing, those three cards are among the cards to be prioritized
Consider its card type, any effect that affects when you could cast it (such as flash) and any other effects that could stop you from casting it (such as Meddling Mages effect) to determine if and when you can do this
Its really cool seeing the interplay of the Affinity cards from the original Mirrodin block with the new colored Esper artifacts from Shards of Alara, for instance
A common choice is Tormod, the Desecrator, or Desecrated Tomb, which create tokens when a creature leaves the battlefield