To ensure tournament demand is similar, I compare cards with similar Standard metagame dominance percentages, that see no Modern play
You can transform it when it attacks, and that also gives your other legendary creatures a small Overrun effect
Not Dead After All is a way to save a creature from dying, as it will return to the battlefield with a Wicked Role token on it
Deck Filters Thanos, Death's Consort 4.5%inclusion 4%synergy 29 decks 642 decks Ultimo, Civilization's End 2.9%inclusion 2%synergy 20 decks 691 decks M.O.D.O.K

Julius Jumblemorph Ego Erasure Feisty Spikeling Firdoch Core Fire-Belly Changeling Flock Impostor Formless Genesis Game-Trail Changeling Gangly Stompling Ghostly Changeling Gladewalker Ritualist Graveshifter Guardian Gladewalker Impostor of the Sixth Pride Irregular Cohort Littjara Littjara Glade-Warden Littjara Kinseekers Masked Vandal Maskwood Nexus Mirror Entity Mischievous Sneakling Mistform Ultimus Mistwalker Moonglove Changeling Moritte of the Frost Morophon, the Boundless Mothdust Changeling Mutable Explorer Nameless Inversion Omni-Changeling Omo, Queen of Vesuva Overlord of the Hauntwoods Personify Prideful Feastling Realmwalker Rooftop Percher Runed Stalactite Shapesharer Shields of Velis Vel Sizzling Changeling Skeletal Changeling Springleaf Parade Stalactite Dagger Taurean Mauler Three Tree Mascot Turtleshell Changeling Universal Automaton Unsettled Mariner Valiant Changeling
you can't cast it without sacrificing a creature, and you can't sacrifice additional creatures