For one, it picks on one player and then leaves that player on the sidelines for the rest of the game
Final Showdown I would not play a six mana board wipe that only hits creatures
This is actually a really interesting card, considering it understood that higher casting cost creatures have better abilities, and that off color cost abilities have to be more expensive
A melded creature's mana value is the sum of its two melded cards
This is pretty straightforward stuff, with the sort of distribution were used to: guaranteed foils of the new sweet lands, guaranteed foils of commons and uncommons in the new frames, a guaranteed foil rare or mythic, an extended-art version of the Commander rares (nonfoil only, a choice I still dont understand) and then the last slot, where the rarest, shiniest things live
Coupled with a bit of interaction for graveyards before sideboarding (Harveys winning maindeck contained Nihil Spellbomb, Tormods Crypt, and Grafdiggers Cage), Whir Prison seems like a well-positioned strategy for as long the metagame has its present shape