ViviVivi adds an amount of mana equal to his power, but only once on each of your turns
Fell the Mighty should let us clear the board of anything bigger than Varina if we choose to target her with it
What's great about this planeswalker commander is there are all sorts of avenues to go down, you've got trample and haste being relevant keywords you want on most of your creatures, burn damage providing a win con if you can make Boo (or your other creatures) big enough, and a renewable token that makes a great target for sacrifice effects
Equip Whenever equipped creature deals combat damage to a player, surveil 2
The same is true for split cards, adventurer cards, and prototype cards
This is another great commander card that goes in Kaalia of the Vast as a way to kill an opponent potentially out of nowhere