@jdoleary
I imagined some kind of structure like a pylon or obelisk. It would be really tanky, and the aura field would negate all incoming damage for all enemy units within it.
Thoughts:
Targeting prevention feels bad and discourages interaction
Damage protection means summons struggle a lot against the pylons (I like this)
Brute force is possible, but it would take a lot of resources since the structure is very tanky
Players could find creative, non-damage ways to deal with the protected units (freeze, enfeeble, suffocate, execute, moving the structure or affected units)
Would be OP as a player summon, maybe shouldn't be capturable
This depends on the Aura task