Mental Misstep was banned in the initial Modern banned announcement, based mostly on how it played in Legacy, where it essentially pushed one-mana plays out of the format and made most decks 56 cards, since everyone had to run Mental Misstep, not so much because they wanted Mental Misstep in their deck but because they needed to be able to counter their opponent's Mental Missteps
That's really good, and 6 mana in Commander is mid to late game
A portion of those can appear in the scarcer Master Ball pattern , which collectors prize even more highly
If you control your commander, this card can often stack up favorably with green finishers like Overrun while also protecting your creatures, giving them lifelink, and keeping them untapped in case you cant finish off everyone in one big swing
Creature cards can be used to attack your opponent and lower their life total