If you're already in the last room, complete that dungeon and start a new one
Its basically Colossal Dreadmaw and Arvad the Cursed all in one
Go Wide decks achieve this by playing team-wide pump spells, or any other effect which affects each creature you control. Youre effectively multiplying the impact of the spell by the number of creatures you control, without paying any additional costs and its not very hard to control a LOT of creatures if youre really focused on it
These are the very best cards in that category: the show-stopping centrepieces that look just as good on the dinner table as they do on your playmat
Hopefully I hit the mark with fun commanders on this list of jank
Inalla, Archmage Ritualist gives you temporary copies of your wizards, Azami, Lady of Scrolls turns them all into extra card draw, and Kaza, Roil Chaser gives you cost reduction based on the number of wizzies you control