After playing with this I realized what the issue is:
Trigger events do not check to see if the colliders are overlapping,they simply check if one unit enters into it. This means that if the unit is not moving, but the projectile is, then the trigger will NOT go off.
For the spells in a game like Soul Saga, what I need is an action that checks if there are ANY colliders intersecting with a specific collider every frame, no matter whether it was spawned on them, someone entered, someone stood still and got entered, etc. (an optional filter tag option would also be nice with this to tag hitbox colliders)
For example, if the enemy is standing still ,the fireball should still hit them. Or, maybe I have a spell with a fireball that moves at first , then sits at a location until someone collides with it (like a bomb). Or Maybe a fireball will spawn on top of an enemy (because it's too close).
There must be a simple way to achieve this, but with the limited knowledge I have this seems like it'd be a very complicated web of collision detection.
Does anyone know how to achieve the results I need?