To have a creature that strong the downside is that you have to discard a card to keep it alive, but in this deck, its not a downside but an upgrade
If you really like the ATK reduction + destruction effect of Slifer the Sky Dragon , King Tiger Wanghu gives you virtually the same effect, and is easier to set up
(Some abilities can also target unexerted cards.) But not using them has less of a direct benefit - you dont need to defend your life points, as in MTG or Yu-Gi-Oh!, so leaving cards upright is typically only worthwhile if theyre likely to be challenged by your opponent and you need them for a future turn
Send 1 Fusion Monster from your Extra Deck to the Graveyard
Now, looking past the obvious picks, heres the stuff power players actually use to dial in runs across games like Slay the Spire : has rotating Monster Train Daily and Expert Challenges that remix mutators and difficulty ladders, perfect for repeatable test runs and score pushes
Despite appearing to be somewhat weak competitively, Sab-Sunen, Luxa Embodied will work wonders in Commander