Onyxia's Lair Boss Guides - Wrath Classic (WOTLK)

Onyxia

Phase 1

Tank Onyxia with your back against the back wall so no one else gets hit by
Wing Buffet
and
Flame Breath
.
Make sure everyone stands on the sides of Onyxia to avoid
Tail Sweep
and getting knocked into her eggs that will spawn Onyxia Whelps.

Phase 2

Starts at 65% and Onyxia will fly up into the air.
Stay at least 8 yds away from other players to avoid
Fireball
AoE damage.
Keep track of Onyxia while she is in the air because she will randomly cast
Breath
, dealing a large amout of damage in a wide straight line across the entire room.
Staying near the sides of the room will help avoid this, but you will need to rotate depending on what angle Onyxia uses it.
AoE the Whelps that spawn.
Tanks pick up the Onyxian Lair Guard that spawns at the entrance of the room. Melee DPS focus these down but watch out for their
Blast Nova
.
Ranged DPS focus on bringing Onyxia to 40% health.

Phase 3

Starts at 40%, Onyxia will land in the center of the room.
Stop all DPS when she lands, and allow the Main Tank to pick her up and get her positioned like she was in Phase 1.
Onyxia will cast
Bellowing Roar
occasionally and spawn cracks in the floor, dealing damage to anyone standing in them.
Onyxia will spawn Onyxia Whelps, AoE them down.

Notes

onyxia's lair Boss Guides - Wrath Classic (WOTLK)