I especially like that you have your own Secret Base, which you get a bit later in the game
Apart from mutate cards to trigger that ability, I guess you could use Stuffy Doll and Brash Taunter, or fill your deck with cards that grant abilities to your commander like backgrounds and the legendary familiars (Kediss, Falthis, et al)
Syr Konrad, the Grim is its own slow wincon if you mill enough
It's an excellent multiplayer mechanic because it allows for creature decks to avoid kingmaking scenarios, or purposefully engage with them in order to play politics or create periods for player interaction
Official rules state that you are not allowed to use proxy cards in tournaments as they require authentic cards as the prizes usually end up being cash awards
negate the activation, and if you do, banish it