Can you force client to see target ring?
 

The basic effect I want to achieve is to have the boss's AoE attack visible before it happens. In my mind the perfect solution would be to have the boss spawn an untargetable invisible NPC at some position which has its target ring visible to all clients in the fight. Then after a set period of time the invisible NPC can cast the AoE and depop. This solution has the benefit of easily changing the size and color of the target ring by altering the invisible NPC's size, and level.

Is anything like that even possible? If not what sort of viable workarounds are there?

I searched through the NPC model list to find some alternatives and the best I could find was race: 705 which is a big ring of water, but at higher sizes it starts looking strange.

Is there a way to spawn those void portals (like the one in potimea) and also alter there size? That might work.

Any help would be appreciated.

live used auras for this. I need to add support for the particle effects still.