If all you want is to find one card you can find it but the Vault offers something more by letting you preview what cards would come along with it, allowing players to plot out the next several turns of the game and see if the sequence being offered would get it done
Jawbone Skulkin + Fang Skulkin I find it a little funny that even non-red decks play Jawbone Skulkin sometimes if they can consistently play it for free
To help determine the rarity, examine your cards carefully
Kenrith often saw play alongside Cavalier of Flame in Fires of Invention decks, where the two creatures combined abilities could increase creatures power and allow them to get through for more damage
Mortal Flesh Is Weak is the worst offender: in the normal archenemy format, it looks at all three of your opponents' life totals and sets the two highest down to match the lowest
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.) Casting a card by using its retrace ability works just like casting any other spell, with two exceptions: You're casting it from your graveyard rather than your hand, and you must discard a land card in addition to any other costs
