Ureni, the Song Unending
Wedge dragons ask a lot and give a lot, but the arrival damage here is scaled to something most bombs leave alone: your land count. Land this off eight lands and you are dividing eight damage across any number of your opponents' creatures and planeswalkers, wiping a board, sniping a walker, or splitting the difference, all before the 10/10 flyer ever swings. Because X grows with the game state, the card rewards the long game rather than the fast one, an unusual reward structure for a body this size. The two-color protection is the sharper design piece, but it is worth being precise about what it does and does not do: protection from white and from black turns off the targeted removal both colors lean on, the exile and burn of white, the point-and-destroy of black, and it also prevents damage, blocking, and being enchanted or equipped by those colors. What it does not stop is the edict, which targets the player and forces a sacrifice, so black keeps one of its cleanest answers to a hard-to-remove threat intact. That gap matters: opponents left without targeted removal have to race the flyer, chump it, bounce it, or make you sacrifice it, and the entry damage has usually thinned their board for two of those already. The rate is enormous and the front-loaded value real; the eight-mana cost and the requirement to actually resolve it are the levers holding it in check.
