Two mana for two 1/1s isn't spectacular in Commander, but you get to tack on another ability for no extra cost
Cast Despair on the next turn with the potential for an opponent to discard up to their entire hand if you have seven or more creatures that dealt combat damage that turn
MTG Defender keyword history The Defender keyword was created in the MTG set Champions of Kamigawa in 2004, but creatures that can't attack have been a part of Magic from its very first release
You can replace Swan Song with Arcane Denial for a relatively small disadvantage
Instead of just one Commander card, you can have two as long as the card has Partner. Combine Leonardo and Donatello to create a token +1/+1 counter engine that will make everyone else at the table lose their minds as you try to keep track of your board
Arno is fine, I guess, and goes in 5c Ezio, Altair, or in non-ACR Rakdos decks