Abilities:

Phase 1 (while Onyxia lives):

Onyxia (starts alone):

• Electric Discharge - When the orbs glows, inflicts 20K nature damage per second to enemies on her sides, increased by Lightning Charge level, can be line of sighted
• Shadowflame Breath - Inflicts 35K shadowflame damage in a frontal cone every 0.5 sec for 1.5 sec, also ressurects Animated Bone Warriors in the aoe.
• Cleave - 110% normal melee damage to enemy and nearest allies
• Tail Lash - Sweeping tail strike hits all behind for 18K damage and stuns for 2 seconds
• Children of Deathwing - Nefarian and Onyxia attack 100% faster if they are within 60 yards of each other

Nefarian (appears 30 seconds later):

• Hail of Bones - Cast 6 times before landing, spawning an Animated Bone Warrior and doing 25K shadow damage to nearby enemies
• Shadowflame Breath, Cleave, Tail Lash, Children of Deathwing - Same as above

Nefarian's Lightning Machine (activates if Nefarian is dps'd):

• Electrocute - Genrates massive bolt of lightning that strikes the ground, inflicts 105K nature damage to all enemy targets

Animated Bone Warrior (starts at 100 energy, depletes and inactive at 0)

• Animate Bones - Shadowflame energy animates these bones, takes 2 energy per second
• Empowering Strikes - Melee and ranged attacks empower caster, increasing damage dealt by 100%, stacks

Phase 2 (3 minutes or Chromatic Prototype's deaths):

Lava

• Magma - Deals 5K fire damage per second, increases damage taken from magma by 2000, stacks

Nefarian

• Shadowflame Barrage - 25K shadow damage to an enemy
• Shadow of Cowardice - Inflicts 30K shadowflame damge to enemy and increases shadow damage taken by 100%

Chromatic Prototype (does not melee)

• Blast Nova - Does 15K fire damage to all enemies every 2 seconds for 30 seconds, interruptable

Phase 3:

Nefarian

• Cleave, Tail Lash, Shadowflame Breath - Same as before
• Shadowblaze Spark - Creates shadowy blaze at nearby location, expands in circular form and follows players and speeds up if touched.
• Shadowblaze - Inflicts 50K shadowflame damage to all in it, resurrects Animated Bone Warriors

Animated Bone Warriors

• Animate Bones, Empowering Strikes - Same as before

Notes:

Phase 1:

• Onyxia starts alone, phase ends when killed
• Standard dragon positions, no stand in front or back
• Electrical Discharge will shoot lightning from her sides, can be line of sighted
• Nefarian will spawn 6 Animated Bone Warriors for you, kite those (undead CC'able too)
• Too much hp to burn, and the become inactive over time
• But revived if hit by shadowflames, so keep them away from those frontal cones
• 30 seconds in, Nefarian lands, tank him 60+ yards away or both get a 100% haste buff
• If Nefarian is dps'd during this phase, occasionally Electrocutes everyone, 100K aoe damage to heal through

Phase 2:

• When Onyxia dies, Nefarian flies up and the room fills with lava
• Get to a pillar swim up and jump out of it
• Divide the raid in 3, each pillar will have a Chromatic Prototype on it, doesn't need tanks
• This phase Nefarian just random blasts the raid
• Meanwhile, each of your teams kill the Chromatic Prototype on their pillar
• Does constant blast waves, interruptable
• Phase ends in 3 minutes or when all Chromatic Prototypes die

Phase 3:

• Lava goes away, and he lands, similar to phase 1 again
• Except, there's now shadowblaze, a purple fire that grows and follows players
• Think Mimiron hard mode fires but way faster, and growing outwards in a circlular fashion
• They also revive the Animated Bone Warriors when the fire inevitiably hits them
• Deal with them the same way, kite/CC til inactive again, if you're able to keep away from fire that long