When playing Commander, a decks commander resides in the Command Zone. A Commander can be cast from the Command Zone for its expected costs, plus an additional two mana for each previous time its been cast from the Command Zone this game
Disney Lorcana is very similar to other trading card games in a lot of ways, but there are also a lot of differences
If you don't remember any blue knights you have access to, try Cavalier of Gales, Thistledown Liege or Herald of Hoofbeats
If you just activate his +2 twice, and then his -3 once, every three turns, then you have discarded two lands, drawn four cards, and put two lands onto the battlefield without taking a land drop
Stiltzkin is cheap and flexible enough to potentially break into Standard, and if not Commander play is definitely on the cards
Finale of Devastation finds you pretty much whatever you need throughout the game and in the later stages offers a pretty easy kill condition