: Search your library for a Dragon permanent card and put it into your graveyard. If you do, Scion of the Ur-Dragon becomes a copy of that card until end of turn. Then shuffle.
Cheat out Scion as your tutor-and-clone engine: tap mana to fetch any Dragon permanent into the graveyard and become a copy of it for the turn, generating massive value or assembling a combo kill. Early turns you ramp and stabilize across all five colors, then snowball into a board of fatties or a Scion-fueled finish. The deck plays like a Dragon-tribal toolbox where you can find exactly the threat the situation demands.
Five-color identity gives access to every removal spell, ramp piece, and bomb in the format
Built-in repeatable tutor that fetches any Dragon for value or combo each turn
Scion's copy ability dodges sorcery-speed answers and can recur powerful ETBs via reanimation
Dragon tribal payoffs reward a critical mass of huge evasive threats
Five colors means a fragile, taxing mana base prone to color screw
Scion's ability costs per activation and only lasts until end of turn, demanding lots of mana
Self-milling Dragons feeds graveyard hate and can deck-thin into reanimator weakness
Commander tax and removal slow the engine if Scion keeps dying
Many lines are mana-hungry and clunky without ramp online
Essential ramp and color fixing to support the greedy five-color mana base.
Tighten the mana base with all relevant fetchlands, duals, Triomes, and fast mana like Mana Crypt and signets so your five colors come online consistently. Add the Worldgorger Dragon plus Animate Dead infinite-mana combo and efficient tutors to make Scion a true win-on-demand engine, and lean on reanimation to skip the -per-turn grind. Round out with premium interaction (Cyclonic Rift, Teferi's Protection) to protect your engine in higher-power pods.
Legendary Creature — Dragon Avatar
: Search your library for a Dragon permanent card and put it into your graveyard. If you do, Scion of the Ur-Dragon becomes a copy of that card until end of turn. Then shuffle.