Illusions are a predominantly blue creature type associated with copying, evasion, and creatures that can be unusually fragile. Several classic Illusions sacrifice themselves when targeted, trading durability for excellent rates.
Phantasmal Dragon offers a large flying body with that familiar drawback, while Krovikan Mist grows according to the number of Illusions you control. Lord of the Unreal neatly solves the fragility problem by giving other Illusions hexproof.