So if I make my commander Captain America, First Avenger (a red-white-blue creature), I cannot use any green or black cards while building that deck
However, this also means he's constantly disappointed by their sub-optimal choices, and he's mostly known for dour strictness and hair-trigger scoldings
Command Tower is one of the most reprinted lands of all time, as its simple ability to be tapped for any mana color your deck has is useful in every Commander deck
Additionally, Naganadel is a very potent non-GX attacker, and has synergy with the aforementioned GX attack that should make it common to be at 3 prizes
Mox Diamonds updated rules text makes it so that the card cant enter the battlefield at all unless you discard a land card, so you cant tap it without having discarded a land card because it just wouldn't enter the battlefield
Draw, discard, flashback