mtg card that changes all creature types I'll let you copy, but change it a bit Morophon, the Boundless · Modern

Phyrexian Obliterator Phyrexian Obliterator limits the number of playable removal spells against it

It also makes a token at instant speed that can pick up a Ghostfire Blade and attack on your turn

The Circle of Loyalty is only for a Knight deck, but it is very good as an anthem and that produces its own threats

The name's a little on the nose, but who can fault that level of nostalgia

But probably the most obvious examples are the Plague Rat and Benalish Hero decks

Example Decklist: Rat Colony in Historic Brawl Rat Colony | Illustration by Suzanne Helmigh Commander (1) Creature (46) Rat Colony x44 Crashing Drawbridge Pack Rat Sorcery (5) Bloodchief's Thirst Echoing Return Reanimate Unearth Agadeem's Awakening Instant (4) Cut Down Dark Ritual Fatal Push Dismember Enchantment (3) Black Market Connections Phyrexian Arena Necropotence Artifact (3) Jet Medallion Bontu's Monument Herald's Horn Land (38) Bloodstained Mire Cavern of Souls Marsh Flats Mudflat Village Nykthos, Shrine to Nyx Phyrexian Tower Polluted Delta Susur Secundi, Void Altar Swamp x26 Swarmyard Urborg, Tomb of Yawgmoth Verdant Catacombs Witch's Cottage I wanted to showcase a deck you can build for relatively cheap on Arena