Flavor Text Goodness, those scarabs are awfully close
Both commander choices are great for the deck, and unlike most cases, where there's a clear "best" commander, the choice between Tidus and Yuna is completely up to personal preference (although Yuna is the stronger of the two)
Its a perfect fit for decks that like casting spells multiple times, like Niv-Mizzet, Parun or Kess, Dissident Mage
(It deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.) Karns creation is now his master
As for Conflagrate, thats a trickier piece of the puzzle
Timmerian Fiends is a 3-mana black creature that can sacrifice itself as a form of convoluted black artifact removal it not only destroys the artifact, but it puts that artifact into your graveyard and makes you its owner