The Mauler is a 4/4 with trample, while the Valesk is a 4/2
You can turn extra lands in your hand into card draw, and bring them back later with one of the various Crucible of Worlds effects in the deck, or with massive land reanimation like Splendid Reclamation
Teferi's Protection While ultimately a defensive spell, if you want to talk about cards that are quite definitionally game changing, this is one of them
The medallion cards, like Emerald Medallion, are staples, but Slime Against Humanity gets even more benefit out of the cheaper Locket of Yesterdays, which will reduce the cost to one green mana after just two other copies are in the graveyard
The Forces of the Imperium deck is all about creating advantages even when it seems like there are none
They did explore the concept of making a Warrior of Light commander players could make their own in some fashion, but Holt says those ideas had some pretty in-depth executions, and that your own personal hero still has plenty of moments in this deck even without being at the helm