Army of One: Soloing Onyxia for Reins of the Onyxian Drake

Army of One is a series featuring tips on soloing fights for chances at vanity items, mounts and pets. I've successfully completed the fights with a melee (enh shaman) and ranged (shadow priest) character, though some classes will experience greater difficulty. I include class-specific advice at the end of the post when requested/needed.

Onyxia. She drops that sexy-looking drake. And the 10-man version of the fight can be soloed by any max-level class at this point. I realize that's a bold statement to make having not actually played through the fight with every single class, but my own experience paired with general interwebz sleuthing leaves me feeling comfortable making that claim. If you experience great difficulty with this fight, please leave a comment! I'd be happy to help you personally and perhaps suggest some alternative tactics.

Naturally, this fight is most easily accomplished at level 90, but some classes should be able to kill her at lower levels. Results may vary. 

Location: Onyxia's Lair in Dustwallow Marsh
Fight Notes: 3 phases (ground phase to 60%, air phase to 40%, then ground phase until death)
Melee concerns: DPS up-time to push through Phase Two, survivability during Phase Three
Ranged concerns: Survivability during Phase Three, burst DPS (some classes)

Ony sports 4.8 million HP, so it won't take too long for most decently-geared level 90 players to cut her down. The key to easily beating this fight is burst DPS. Pushing her through the phases quickly means the player will take a minimal amount of damage. Note: classes packing heavy burst my be able to push Onyxia to Phase 3 without even having to deal with the Phase 2.

Phase One
Pre-pot, or consume an on-use stat potion for your class just prior to pulling Onyxia. Since you've consumed it before entering combat, you'll be able to use a second potion later on in the fight once it comes off cooldown. I usually use one or two damage cooldowns each phase to make it go smoothly. Other classes' experience may vary depending on the number of cooldowns at their disposal.

Beat on Onyxia. Tip: before she takes flight, which signals the start of Phase Two, she will lumber over to the entrance of the room (where you first engaged her from). To increase maximum DPS up-time for Phase One and reduce the amount of HP to cut through in Phase Two, fight Onyxia all the way on the opposite side of the room from where you entered. The few extra seconds of DPS while she's running back across the room at the transition into Phase Two can mean a few extra hundred-thousand hit points shaved off, which can be very helpful to melee, since they'll have a more difficult time damaging her once she's in the air.

Phase Two
She's now in the air and whelps will hatch and beeline for your location. She also summons an additional, stronger add every 30 seconds. The key here is staying alive while pushing her to Phase 3 as quickly as possible. I use damage reduction or healing cooldowns if needed, and usually pop another damage cooldown. You're doing it quite well if you push her to Phase 3 before she summons a guard. Melee with limited ranged abilities should focus on staying alive and burning through adds, saving any ranged abilities for damaging Onyxia.

Once again, DBM will indicate an impending transition to Phase Three. Onyxia will begin to fly to the side of the room opposite the entrance (if she's not already there). This is where she will land for Phase 3.

Phase Three
Use another potion if off cooldown. Otherwise, your main objective here is to kill Ony before she and her posse kills you. She'll fear you every so often, so if you have an ability to counter that, use it. Otherwise, it's only a matter of time before the whelps will overwhelm and you will die. Use passive AoE to knock out some or all of the whelps if you have low survivability; they will die easily. If you're not concerned about your health, you can safely ignore them. Pop any remaining damage cooldowns and Ony should die without giving you too much to worry about.

Good luck on the drop!