Having a smaller cube also offers some material benefits: You dont need to buy as many sleeves or cards, and the cube will be easier to transport, shuffling after playing is easier, etc
Partner (You can have two commanders if both have partner.) Legendary Creature - Kraken Color tag templates(None) Fierce Empath When this creature enters, you may search your library for a creature card with mana value 6 or greater, reveal it, put it into your hand, then shuffle
Quantum Misalignment, an expensive clone effect, but worth mentioning due to how popular Irenicus's Vile Duplication is
While damage can still accrue if your opponent has a card with a 'damage can't be prevented' effect, that damage still can't be dealt until the Terefi's Protection has been lifted on your next turn, and your lifetotal can be adjusted again