mtg 20 ways to win bonus card Secret Lair Commander Deck: With the new “20 Ways

The longer a bounty goes unclaimed, the bigger your eventual payoff but dont get so greedy someone snatches it out from under you

There are no sideboards, and therefore no opportunity for selecting a companion or utilizing effects that reference outside the game (Masterminds Acquisition, Fae of Wishes, etc)

To figure this out, you need to think about what's going to matter in this game as a whole, as well as ask some questions about what you know of your own deck

Put these two things together, and the most obvious answers are Uro, Titan of Natures Wrath and Kroxa, Titan of Deaths Hunger from Theros Beyond Death