Outside of the set, treasure has taken up residence in many a deck, along with other artifacts you might want to sacrifice
Once on the board, their abilities allow them to generate massive amounts of momentum while protecting each other from opposing challenges
If you can do weird life total stuff, though, this could be a fun puzzle piece
It's clear via the reporting from IGN and the comments made by Holt and Deveny that the team at WotC has a great love for this franchise, which in part led to the choices of Final Fantasy VI and Final Fantasy X due to the places those games held in the team's hearts
They copy themselves for each spell cast before it, so it's possible to cast enough spells to burn all your opponents with Grapeshot, or mill them all with Brain Freeze if you're able to cast a ton of spells in one turn (made easier with the Hullbreaker Horror combo)
Ability costs can include ink (paid by exerting cards in your inkwell), exerted cards (paid by, well, exerting cards) or something else explained on the card itself