Thaddius Thaddius is the fourth and final boss of the Construct Quarter in Naxxramas . 25 - man abilities . Feugen and Stalagg . The encounter begins with splitting the raid in two to engage Feugen and Stalagg . If they leave their platforms ( or are even just pulled too close to the ramp up to their platforms ) the entire raid will be hit by unhealable massive nature damage from the Tesla coils in the room . They have 2 , 100 , 000 HP each . If they are not killed within 5 seconds of each other they will resurrect each other with full health . Feugen . Hits for about 4 , 500 on plate . Stalagg . Hits for about 6 , 000 on plate . Thaddius . After Feugen and Stalagg are slain the raid has 15 seconds to jump to Thaddius ' platform before Thaddius becomes active . Thaddius has approximately 30 , 400 , 000 hit points . This damage buff is needed to have any hope of killing Thaddius before his berserk . Cast every 30 seconds . THERE IS NO PATTERN TO WHICH RAID MEMBERS GET WHICH POLARITY ! 10 - man abilities . Feugen and Stalagg . The encounter begins with splitting the raid in two to engage Feugen and Stalagg . If they leave their platforms the entire raid will be hit by unhealable massive nature damage from the Tesla coils in the room . They have 838 , 300 HP each . If they are not killed within 5 seconds of each other they will resurrect each other with full health . Feugen . Hits for about 3 , 000 on plate . Stalagg . Hits for about 4 , 500 on plate . Thaddius . After Feugen and Stalagg are slain the raid has 15 seconds to jump to Thaddius ' platform before Thaddius becomes active . Thaddius has approximately 3 , 850 , 000 hit points . 25 - man strategy . You will want two tanks . Thaddius and his adds are tauntable . This encounter is significantly harder on 25 - man mode , as the enrage timer becomes a very restricting factor should you lose raid members early . Even losing non - DPS classes is harmful , due to the loss of a stacking + 10 % damage buff . The Thaddius portion of the fight is typically very easy to heal , usually requiring no more than 3 - 4 healers for a 25 - man raid . Any remaining healers should help DPS to beat the enrage timer . Phase 1 : Feugen and Stalagg . Phase 1 is very simple . Split the raid into two groups that will deal approximately equal damage , with half the tanks / healers on either side . Keep the tanks alive and heal Feugen ' s / Stalagg ' s damage , keep the adds on their platforms , and kill them simultaneously . Tanks should be certain to keep Feugen and Stalagg in the middle / back of their platforms and within range of the Tesla coils - shifting too far towards the base of the ramp can pull them out of range , causing unhealable nature damage to the room and wiping the raid . Every so often , the tanks will be " thrown " to the opposite platform , and their accumulated threat reassigned to the new mob . Tanks may need to pull back and reposition slightly after being thrown to the opposite platform . At around 5 % it is necessary for both groups to check where the other is on damage . If either Stalagg or Feugen are killed while the other still has more than 5 % to go , both Feugen and Stalagg will be resurrected and the fight will begin anew . Phase 1 . 5 : The Platform Jump . As soon as Feugen and Stalagg are down , the raid should jump to Thaddius ' platform . It is important to note that this jump is difficult for some people . If one or more members of the raid fail to make the jump , they can run around to the front of the room , up to Feugen or Stalagg ' s platform , and try again . However , any raid members who arrive on Thaddius ' platform after the fight begins must wait for a Polarity Shift before moving near the rest of the raid . Having no charge ( because you were out of range for the first Polarity Shift ) will still trigger polarity charge damage , because the charge is not the same as the other members of the raid ( i . e . , " no charge " is viewed as a different charge than + or - ) . A member arriving late to Thaddius ' platform will thus need to wait , away from the rest of the group , until a Polarity Shift occurs and a charge is received , and the raid member can then join the rest of the raid on the appropriate side . After 3 . 0 . 8 , priests can cast Levitate and mages can cast Slow Fall on anyone in the raid . Players who have trouble jumping down should ask a priest or mage to buff them after Feugen and Stalagg are dead so that all they have to do is run off the edge and float safely down to Thaddius ' s platform . Phase 2 : Thaddius . Thaddius will become active a few seconds after the group reaches his platform , and should be tanked in the center of the platform where he is , but slightly forward so that there is room for the raid to see where to run on either side of him during the Polarity Shifts . Approximately 10 seconds after Thaddius becomes active , he will cast his first Polarity Shift on the raid . The raid will need to immediately stack up in two separate groups depending on their charge . Raid leaders , make sure you clearly state what side the Negative group is on and what side Positive is on ! Each group should clump up at maximum melee range . This allows members with the same charge to buff one another and allows melee DPS to engage Thaddius , all while avoiding shocking members of the opposite group . Stacking the charges is critical , as each charge provides a + 10 % damage buff ( up to 12 stacks ) that will be necessary to defeat Thaddius before the enrage timer . The tank should rotate around Thaddius to match the group that shares his charge . Some raids may prefer to use a front / back arrangement , with ( for example ) negative against the wall and positive on the edge of the platform . This ensures that the groups are tightly bunched for the damage buff , and allows anyone coming in late to go directly to the right place without running through the opposite - charged players . When Thaddius switches polarities again , everyone that has to move should move to the appropriate side as fast as possible . One strategy is to ask everyone to run around him either clockwise or counter - clockwise to avoid shocking players running the opposite direction . However , there are only about 4 seconds between the polarity shift and the first shock , so some raids opt to have members run straight through Thaddius to their new spots . Note that not every Polarity Shift will change the charge on a raid member , so the raid members will need to monitor their debuffs each time Polarity Shift is cast . Once the raid is back in position and stacked with others who have a similar charge , the fight continues as before . This is the entire fight from 100 % to 0 % - there are no phases . You have six minutes to get through Thaddius ' 30 , 400 , 000 HP . This enrage timer is quite strict and it is highly unlikely you will be able to beat it if you lose more than a few people , both because of the lost DPS and because fewer members of the raid alive means there are fewer people to stack to receive the same - charge buff ( thus , even a healer death can become somewhat problematic ) . Once Thaddius is down , the charges immediately dissipate . Thaddius has a quite large hitbox , so it is possible for your ranged DPS and melee to group up relatively close to each other . This positioning has three benefits : If the need for a battle rez arises , the target of the rez should wait for Thaddius ' polarity change and accept the rez immediately upon Thaddius ' cast , then move to the appropriate group . Prematurely accepting the rez will lead to group damage and the target of the rez dying again , thus wasting a valuable resurrection . It is no longer possible to use two Bloodlusts / Heroisms during the Thaddius encounter , because the Sated / Exhaustion debuffs now last for 10 minutes , which is longer than the enrage timer . It may be easier to look at the color of the debuff rather than the symbol , as that can slow reaction times by a fraction of a second . Negative is red , positive is blue . 10 - man strategy . The 10 - man strategy is exactly the same as the 25 - man strategy . The tanks , healers , and DPS are split to kill Feugen and Stalagg simultaneously , and then Thaddius is engaged and the raid begins its rotations after the first Polarity Shift . Thaddius only needs one tank , so have your other ( s ) DPS . Phase 1 : Feugen and Stalagg . Notably , the pacing of DPS on Feugen and Stalagg may have to be monitored more carefully in this version of the fight . For a 10 - man group running 2 tanks , 3 healers , and 5 dps , splitting the raid will mean that one side has more DPS than the other . Consequently , DPS on one side may need to slow down for a brief period of time , to ensure that Feugen and Stalagg are killed within 5 seconds of each other and do not resurrect . Feugen and Stalagg can creep forwards on their platform at times , so it it wise for the tank to reposition their new target at the back of the platform after each tank switch . Phase 2 : Thaddius . The technique for this encounter simply involves assigning a direction to each polarity . As you look in the room before you attack the two mini bosses , you will see Thaddius . The left and right sides as you are facing him are what is referred to by " left " and " right " when sides are called out . When you pull Thaddius and the raid has no charge , stack up on the tank . Then when he casts the first Polarity Shift , run to the assigned side . You only need to get this bit right once ! From then on , the fight becomes simple . Stack on top of each other at max melee range . Thaddius ' s huge hitbox assures that everyone in each group gets the buff , is close enough to quickly change sides , and can be well out of range of the raid members with the opposite charge . When Thaddius changes polarity again , you must look carefully - if your Polarity has CHANGED , run around the boss in a counter clockwise direction and stack on the other side . If it didn ' t change , STAY WHERE YOU ARE ! Continue this for 4 - 5 minutes and you will either kill him or kill yourself depending on how well your group has mastered the movement technique . This technique requires fast reactions and good awareness of de - buffs . If you are part of a group that successfully downed Grobbulus , you are likely to be able to do this encounter . In 10 man , if one person messes up , this does not mean a wipe . If you are unsure where to go , move out of melee range and stand as far away from the boss and both groups as possible , until you understand the mechanic . Quotes . The following quotes ( echoing screams would probably be more accurate ) are heard echoing throughout Naxxramas in addition to during the fight with Thaddius , and will stop after Thaddius dies . The screams sound like those of a woman or child :