|Defeat in The Oculus on Heroic Difficulty without anyone in your party using an Amber Drake.|
2 Ruby, 3 Emerald
Two ruby drakes will be used to switch tanking during an enrage phase. Two of the three emerald drakes will be dedicated healers while one is occasionally healing but mostly keeping the Touch the Nightmare debuff on the boss which will reduce the workload of healing through enrage damage. Whelps will never be an issue with both ruby drakes constantly spamming Searing Wrath on Eregos. Remember to have tanks switch off aggro in the middle of an enrage, keep up Touch the Nightmare, and this achievement can be done with ease.
See also Edit
Patch 3.0.8 (2009-01-20): 1) you can no longer re-enter the instance during the fight and summon your drake. Re-entering puts you into combat instantly. Re-entering the instance after a wipe is unchanged.
2) you can no longer kite the adds that Ley-Guardian Eregos summons. The adds now have a 300yd range with their arcane barrage spell.
3) You can no longer get Ruby Void and Amber Void achievements in the same Heroic Oculus run.