Vigilante
The Blue Spirit was considered by some to be the protective spirit of Ba Sing Se. It appeared in the outer rings on moonless nights, its twin dao swords seeming to shine with an inner light. People left offerings to it on those nights, small pictures or trinkets, hoping it would be enough to convince it to protect them. It seemed to work, at least. If you asked the people in the outer rings of Ba Sing Se, it was a spirit of protection, of helping those who needed it most. But, if you asked Zuko, it was an escape.