Onyxia's Lair

Onyxia

The four Onyxian Warders in the entrance tunnel cast Fire Nova around themselves: pull them one at a time so only the tank takes it. Phase 1 (100% to 65%): the main tank runs in, turns Onyxia to face the north wall and holds her there. Everyone else waits a few seconds before attacking, because her threat cannot be fixed by a taunt. Melee stand at her flanks, never in front (Flame Breath, Cleave, Wing Buffet) or behind (Tail Sweep, which can throw people into the whelp caves). Ranged and healers spread along the side walls. Knock Away costs the main tank a quarter of their threat, so damage dealers watch their own.

Phase 2 (65% to 40%): she takes off and hovers. Melee cannot hit her with normal attacks. She throws Fireballs at players, hitting the target hard and splashing anyone nearby, so spread out. When she announces a deep breath, she sweeps fire along her head-to-tail line across the room: anyone in the middle dies, so move to either side of that line at once. Whelps pour from the side caves, a large wave at the start and smaller ones after; the two whelp groups hold the cave mouths and burn them down with area damage. Never walk near the eggs, which hatch more. Stop damage near 40% so the tanks can rebuild threat before she lands.

Phase 3 (40% to 0%): she lands and uses her phase 1 abilities again, plus Bellowing Roar: every 10 to 30 seconds the room shakes, the whole raid is feared, and lava erupts from the cracks in the floor. Fear Ward and Tremor Totems keep the tanks in place. Ranged players can stand in the middle of the room, which has fewer cracks; keep away from the egg caves, since a fear can carry people into them and hatch a flood of whelps.

In short: face her to the wall, spread for Fireballs, step off the breath line, kill the whelps and ward the tanks against the fears.