Zaritha, Oathsworn

Vigilance
When you cast Zaritha, declare a card type.
Spells of the chosen type cost all players {2} more
to cast.
Whenever Zaritha attacks, if you have cast a spell
of the chosen type, Zaritha gets +X/+X until end
of turn, where X is the mana spent to cast that
spell. Creatures can only attack you if their controller has cast a spell of the chosen type.