You cannot enter Onyxia’s Lair without the Drakefire Amulet, and you only get the amulet by finishing a long attunement chain. The two factions take different routes. This is the shape of it so you know what you are in for. Your in-game quest log is the final word on exact steps and names.
The short of it
- Both chains run you through the Burning Steppes and Blackrock, with at least one Upper Blackrock Spire (UBRS) run involved, which is a 10-player dungeon.
- Plan on a few play sessions, not one. Some steps want a group, some want travel, and a couple are easy to miss if you skip quest text.
Alliance route
Your chain centres on freeing and helping Marshal Windsor and then exposing the dragon hiding in Stormwind.
- It runs through the Burning Steppes quests and a UBRS step, then moves to Stormwind for the finish, where you take part in a scripted event in the throne room.
- Read the quest text. The Stormwind finish is a set-piece and people who run ahead miss it.
Horde route
Your chain runs through Kargath and the Burning Steppes, with a UBRS step, and ends with you earning the amulet from your faction leadership in Orgrimmar.
- Same advice: do the Blackrock steps with a group already going to UBRS, so you fold the dungeon part into one trip.
Practical tips
- Do the attunement the same week you start raiding, not the night of the raid. Forty people waiting while three of you finish a quest chain is a bad raid night.
- Bring quest items and turn-ins with you, the chain bounces you across the world more than once.
- If you fall behind your guild, ask in your guild chat. Someone has almost certainly just done it and remembers the annoying step.
Once the amulet is on, you are in. Onyxia herself is a separate write-up.