This is a named mob in the Plane of War. For an overview of all nameds in the Plane of War, their PHs, map points, and mapped locations, see this quest entry.
The Judicator can spawn upon the death of any mob in the Field of Strife. Its spawn seems to be somewhat fixed with perhaps some randomness thrown in. Group members will see emotes ahead of its spawn about "flapping wings in the distance" (the first emote seen) and "sound of wings grows louder" (second emote, indicating its spawn is closer). There is significant variation in reported kill counts (anywhere from 22 to 39 kills, with 31-35 being the average).
It has ~37 million hitpoints; hits for a max ~20,000; AE rampages; and casts a directional (sides) AE knockback every 20-60 seconds. It also has an aura called "Weakened Defenses" which negates defensive abilities.