Egwene, Flame of Tar Valon

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

The first instant or sorcery spell you cast each turn
has convoke.
(Your creatures can help cast those spells. Each
creature you tap while casting the first instant or
sorcery spell each turn pays for {1} or one mana of
that creature's color.")