Aura collision object is a (typically spherical) object that is centered on the aura source, allowing enemies to collide within/with the object. The visual aura can be a different display object that is purely cosmetic.
The implementation allows versatile behaviors that allow to create unique auras/effect, collision delays, collision radius,etc(example: rotating firewall object dealing splash damage on collision, circle of blade objects, etc essentially collision objects orbiting/rotating around the player).
A.Normal damage collision. Aura deals damage to colliding entities once per collision check interval.
B.Effect damage(e.g. knockback). Owner of aura launches fast invisible tracking projectile to target that delivers the effect.
C.Anti-projectile aura. Colliding projectile properties(speed, damage) are modified.
D.Defensive aura. AoE attacks/Curses/effects within the collision sphere are nerfed(often multiple times).
E.Healing aura. Does negative damage to allied entities colliding with it(see #A).
F.Transfer aura(e.g. stat leeching). Enemies stat X is reduced on collision and sent to owner of aura.