To maximise the power of Mental Misstep in a deck you are advised to have some filer and/or card quality effects so that you can replace it once its value is diminished
15 to 22, with the set arriving on Magic Arena Jan
While it is niche - there needs to be a reason to have this in a Tron or Eldrazi sideboard, for instance - when it's powerful, it's really powerful
Legendary spells and payoffs are a key part of so many new sets that you can build legends-matter decks across a variety of different color pairs without much overlap
Are you planning on playing Vibrant Cityscape in any decks, and if so, are you taking out Evolving Wilds for it
Humans are one of the deepest kindred types, and though six is a lot to earn the extra card, owyn, Shieldmaiden helps you get there quick since the ability triggers on any humans, including tokens