Solasta: Crown of the Magister

If you have a cleric in your party, Spirit Guardians and Sacred Flame are excellent spells for this achievement. Sacred Flame is a single target cantrip but Spirit Guardians is an AoE that persists around the caster for many turns in combat, dealing radiant to any who step into or start their turn in its radius, making it a great choice for this. I used Spirit Guardians almost every fight, regardless of this achievement, so it should come naturally to anyone using a cleric.