Selfless Savior, Skrelv, Defector Mite, and Mother of Runes are examples of mana-free protection that we can cast before casting our commander (protection from color can also double as evasion!), and we also have cards like Brass Squire which can equip protection for free
At the beginning of each upkeep, if a player cast two or more spells last turn, transform this creature
It lets you keep good one landers
Green Creatures Diamond Weapon: Maybe it takes a little work to be able to cast this creature for a reasonable amount of mana - but I think youll be able to cast it on turn six without a lot of effort, and even sooner if you build a deck focused on self-mill
Then, if CARDNAME has no doom counters on it, sacrifice it and put a 5/5 black indestructible Demon token with flying onto the battlefield under an opponent's control
Temporal Cascade or Reminisce, for example, are important in order not to perish due to a missing library