Cage Rematch is an achievement earned by ensuring that no member of the raid group leaves the inner circle of the encounter room during the encounter in the Nighthold instance, on Normal difficulty or higher.
The boundary of the "inner" circle of the room is marked by the dark blue ring, leaving which will cause the achievement to fail. Be aware that getting knocked back by Skorpyron's Shockwave ability will forfeit the achievement, so ensure that all members of the raid get behind the exoskeletal pillars in time.
A short period of time at the beginning of the encounter is given to allow the party to actually fully get inside the inner ring.
- Patch 7.0.3 (2016-07-19): Added.