At its most broken, the Baron Von Count deck is probably an Ad Nauseam Storm combo deck a la Maralen of the Mornsong, where one player will die as a result of the Counts ability, and the rest will fall to Grapeshot or Tendrils of Agony (none of which is particularly problematic for me, by the way)
So yes: play pieces and testing, great
Each room as you journey through Undercity has nice effects for various Commander battlefield states, and the final room is going to be awesome for most Commander decks that play a reasonable number of creatures
, : Target creature can't be blocked this turn
Exdeath, Void Warlock On the face, a 3/3 with a bit of life gain is only okay, but come the mid to late game, he transforms into a 6/3 or bigger trampler to put the game away