Any card from all of MTG is legal to play in your deck (technically making it an eternal format), other than the formats banned and restricted cards
I went 3-1 with a cool Golgari deck Ive been calling Knight-Time Cat Food
Added Geno, Star Warrior
You have cards that make lots of Vampire tokens (like March of the Canonized, Mavren Fein, Charismatc Conqueror, and Sorin), cards that make Vampires bigger (like Legion Lieutenant, Etchings of the Chosen, and Radiant Destiny), as well as cards to keep your Vampires in play (like Timothar, Kindred Boon, and Dusk Legion Lieutenant)
Terra Branford / Urza, Lord High Artificer (FCA) $28 Magic's most famous character, Urza, Lord High Artificer is also one of the top cEDH commanders, among the strongest artifact commanders, and hands down the best mono-blue commander