This boss is divided into 3 phases. The first and third phases are not DPS intensive but the second phase requires a DPS burn.

The first phase is just like any other tank and spank phase. The damage is severe, but it should be healable with Flash Heal spams. Mana is not a problem since his hits take away more than 10% of maximum health, hence activating Masochism. The only mechanic to watch for is the occasional knockback, which can disrupt any heals being cast. Spam Flash Heals while keeping dots up should be the general strategy to get past this phase.

The second phase starts when the boss reaches 65% health and he will begin the phase by flying into the air. This is followed by a massive group of whelps spawned from nearby eggs. These whelps will need to be AoE'd down. These whelps serves as the major brickwall priests face in this encounter, and being able to successfully defeat these whelps is a huge step forward to defeat the boss. That is not all however, as a second pack of whelps will spawn a minute later and they will too need to be AoE'd down. Aside from these whelps, an Onyxian Lair Guard will also spawn once every 30 seconds during phase 2. These hit rather hard so they need to be killed before they come within melee range. Fortunately they don't have too much health and can be burned down rather quickly. The whelps and the lair guards will continue to spawn until Onyxia reaches 40% health. From personal experience, at 390 ilvl, a priest can at most handle 2 packs of whelps and 3 Onyxian Lair Guards, hence the boss must be pushed into phase 3 as quickly as possible.

Phase 3 begins with the boss landing again. This phase is similar to phase 1 except the knockback mechanic is now replaced with a fear mechanic. Any adds remaining from p2 should be killed ASAP. Minimizing damage taken during fear is important since heals cannot be cast while the player is feared. Rotate CDs such as Fear Ward, Shadowfiend and Dispersion to handle the fear. However, the fear is casted often (every 30s or so) so some fears must be lived through without and CDs. DoT the boss and spam Flash Heals and win.


Tips to burn down the whelps:
1. Use a pot, or a trinket proc prior to AoE
2. Empowered Shadows buff affects Mind Sear, so maybe sneak in a Mind Blast on the boss before the whelps spawn
3. Precast PW:S before the whelps spawn
4. Dont stand in the middle of the room to AoE whelps. Damage taken per tick of Mind Sear is reduced when there are more whelps. Using this logic, it is advised to stand on one side and AoE down one side of the whelps first.



PS - If you are wondering why in P3 I kept my health topped off above all else, it is because I wiped once when he Feared me while my health was on around 60%, during the fear he double crit me for 50k each, killing me of course. Lesson learned.