If the statue in the center island of the zone is facing the Nature tower, this named can spawn from the death of any mob (spawns a distance away and is not auto-aggro). It's reported that it can drop any item of loot from the Nature tower.
For anyone wondering how you're going to find the peacekeepers in each tower, once the center statue is facing the tower you need, go to that tower and head to the 2nd floor where each tower has an "arena". Kill everything in the arena ONLY. It usually only took about 2-3 full clears of the arena for the Peacekeeper to show themselves. They do not have a "PH" per-se as everything you kill in each tower has a chance to get them to spawn, so the easiest way is to simply clear the arena area over and over until they show.
The statue rotates approximately every 48 1/2 minutes. The cycle it followed while I was there was Arcane (NE), Shadow (SE), Nature (SW), Light.(NW).
While I was killing in Shadow with no one else in the zone, Peacekeeper of Anriella (Nature) spawned. It happened near the time of rotation, so I might have killed after it rotated and my kill in Shadow triggered it to spawn in Nature.
If the statue in the middle (at portal in) is facing the nature tower It will spawn this named on the death of ANY mob, and no its not instant arrgo he spawns close to you tho. There is a zone wide Emote that tells you when the statue is facing a different tower. obviously there are 4 towers.
Also Peacekeepers can drop ANY loot that drops from any named inside that certain tower.