Nefarian ( Blackwing Descent tactics ) Nefarian is the last boss of Blackwing Descent , a raid shipped with " " . He can be found in the Vault of the Shadowflame , where he resurrects his sister Onyxia , who makes up the first phase of the fight . Throughout the fight , Nefarian has several other undead adds as well . Nefarian was the last boss of the entry tier of " Cataclysm " to be killed on normal mode , in part due to a respawn bug . The world first kill came on 13 December 2010 , almost a week after the expansion ' s release . It was completed on 10 - person mode by the Russian guild Exorsus . The world first heroic kill was on 10 January 2011 by Paragon ( 25 person ) . Abilities . Throughout the entire encounter every 10 % of Nefarian ' s health will cause Nefarian ' s lightning machine to strike the raid with Electrocute . " Nefarian ' s Lightning Machine " Phase One . " Onyxia " - 6 . 6 million ( 10 - man ) / 24 million ( 25 man ) HP " Nefarian " " Animated Bone Warrior " Phase Two . " Lava " " Nefarian " " Chromatic Prototype " Phase Three . " Nefarian " " Heroic Mode Only " " Animated Bone Warrior " Strategy . Phase One . The encounter begins with an introductory event in which Nefarian ( as Lord Victor Nefarius ) resurrects Onyxia . He then turns into his dragon form and flies into the air , landing 30 seconds into the fight . Before Nefarian lands he will spawn 6 / 12 ( 10 / 25 - man ) Animated Bone Warriors which can be either kited , CC ' d or tanked until they run out of energy and die on their own in this phase . But , they cannot be feared . Onyxia and Nefarian should be tanked on opposite sides of the room to remove their 100 % haste buff Children of Deathwing . Onyxia should be damaged down to low health but not killed . This will give you some time to burn Nefarian ' s health down before the last phase . Onyxia will eventually hit full energy and instantly kill the raid , and every 10 % of Nefarian ' s health adds 25 % to her energy charge . You will generally have time to burn Nefarian down to sub - 80 % before killing Onyxia and ending the phase . Do not let either Dragon breathe on the Animated Bone Warriors as this will break CC , snares and roots and reset their energy to full . Phase Two . The arena will fill with lava and three Chromatic Prototypes will spawn on each raised pillar of the room . They do not melee . They cast Blast Nova which must be interrupted . Assign players to each of the three platforms for phase two . Each platform needs one reliable interrupt for 10 - man and two reliable interrupts for 25 - man ( you will need interrupt rotations on 25 ) . A ranged interrupter is helpful in the beginning of the phase on each platform while everyone is jumping up . It is important to spread out around the edge of the platforms in phase 2 as splash damage from Shadowflame Barrage will cause deaths . You should try to damage Nefarian below 70 % in this phase , survival cooldowns should be used to mitigate the electrocute at 70 % . The phase will end after the Chromatic Prototypes die or after three minutes . TIP : Jumping onto the Pillar platform If you are having trouble jumping onto the pillar , during the transition into Phase 2 , position yourself just a few yards from the pillar . As the lava rises , hold down spacebar ( or your assigned jump key ) until you are leveled with the top of the platform , then press " W + Space " ( forward + jump ) . Phase Three . The lava will subside and Nefarian will land , stay spread out until Nefarian has stopped casting Shadowflame Barrage . Phase Three is like phase one except Nefarian will now cast Shadowblaze Spark , it will always be targetted on the location of the Animated Bone Warriors . It will break CC , snares and roots on the Animated Bone Warriors and reset their energy to full just as the dragons ' breath does . Since Shadowblaze Spark is always targetted on the Bone Warriors , CC and roots are ineffective . You should have a tank kite the Bone Warriors away from Nefarian and continually move to avoid the Animated Bone Warriors ever regaining energy . They will die after 50 seconds and reset their empowering strikes stacks , this will allow the Bone Warrior tank to survive . Both tanks will need to use a survival cooldown to survive Electrocute every 10 % of Nefarian ' s health . The longer Nefarian takes to die the faster he will cast Shadowblaze Spark , until it is impossible to avoid and the raid dies .