Phantasmal Dragon

The bargain on every Phantasmal creature is the same: an undercosted body in exchange for a glass jaw, and here the body is a four-mana 5/5 flier with the durability of a 2/2. The illusion drawback is one of the cleanest pieces of design tension in the bestiary, because it changes the price of removal rather than the type of it. Any targeted spell or ability becomes a free answer: the opponent does not have to kill the dragon, only point at it, and the sacrifice trigger does the rest. A Doom Blade that would normally trade for a 5/5 instead detonates it for one mana; a tap ability or a bounce spell or a single point of incidental damage attached to a targeted effect ends the threat outright, sometimes at a profit. The flip side is that anything which does not target has to beat the body honestly, so a sweeper still has to actually destroy it and combat math still has to get through five power in the air. The cruel symmetry is that your own toolbox is just as dangerous: a friendly pump spell or protection effect detonates the creature exactly as an enemy's removal does, which means the controller has to win the race rather than dress the dragon up. That single line of text rewards interaction so thoroughly that it does more strategic work than the flying ever will.