Utility/damage type spells where you can summon crows to distract and attack enemies or pick up gold/souls/bottles/ammo for you. The final spell you unlock could be a "raven form" that's a short but powerful version of the waiting-to-be-revived "soul form": pass through enemies without taking damage as a murder of crows and damage enemies, pickup any bottles/ammo that you pass over.
(Saw another post mentioning spell synergy. While these wouldn't synergize with fire/elec/acid, they would pair well with any Voodoo spells that leave candles on the ground, as the crows would pick them up, too).
#Crow/Raven Spells
plucky stream
vast sphinx
great ideas! I think some spells could be designed as area damage over time, or you call a gaint crow to carry you flying over some terrains.