Illusory Angel

A 4/4 flier for three mana is well above the curve, and the casting restriction is what pays for it: you cannot lead a turn with this card, only follow one. That single clause reorganizes the entire turn around it. The body wants to land cheap and early, but the gate forces a setup spell first, so the natural home is a deck already casting a stream of low-cost spells (cantrips, cheap tempo plays, anything that fills the prerequisite without spending much). The tension is real: the cards that satisfy the condition most easily are the ones a tempo deck wants to be casting anyway, which means the Angel rewards a build that was already operating on volume rather than asking you to bend toward it. Note the Illusion subtype carries no drawback text of its own here, so the usual "sacrifice when targeted" liability of blue's illusion lineage does not apply; what you get is a clean, oversized evasive threat whose only cost is sequencing discipline. It is a payoff dressed as a creature: the spell that turns a turn full of small actions into four evasive damage, provided you remember it has to go second.