Hydross the Unstable Hydross the Unstable is the first boss of Serpentshrine Cavern in Coilfang Reservoir . He seems to be forced to guard and is being held prisoner by Lady Vashj . He is kept in check by the two beams in his prison . If he leaves them , he becomes poisoned , causing him great pain . Although being the first boss raids meet when entering the instance , The Lurker Below is an easier kill , and it is possible to sneak past Hydross . Therefore , new raids usually try Hydross second . It ' s not know if he is a Neptulon ' s Water elemental ( capture in Azeroth ) or Aborius . Preparation . Raid Composition . The frost tank has to take slightly more damage than the nature tank . Positioning . The melee group needs to move with Hydross , on each phase change a few yards forward and backward . All other raid members should set up distributed , to reduce the effect of Water Tomb . It ' s also no problem to run through Hydross and set up on his back . Starting the Fight . Prior to the pull a small group ( one off - tank , a few damage dealers and a healer ) need to pull and kill enough of the tainted water elementals on the " assembly line " , so that none of them take part in the fight as adds . After the fight has started the tainted water elementals stop spawning . Hydross starts in his water form . Whenever he leaves the area where he stands initially , he switches to the poison form . When he ' s moved back into the two beams , he switches back to the water form . Form switching takes place whenever he crosses a " magic boundary " which runs approximately between the two small flags in front of him . Every time he switches form , four adds of the same type as his new form are summoned . If pulled conventionally , Hydross would immediately switch to the poison form and summons adds . Druid tanks can simply use Feral Charge and start the fight with a full rage bar . If druid is off - tank , main tank taunts aggro from him . The safest method to avoid this is to use a Lesser Invisibility Potion . The frost tank has to wait until he drops out of combat ( because he is in combat due to the assembly line adds being killed ) , use the potion , walk into melee range and start the fight from there . Another possibility is to use a combination of Swiftness Potion and Intercept , to reach him fast enough before he crosses the boundary . As a third safe method , a mage can use Invisibility , walk behind Hydross and Ice Block there . Hydross aggros on the ice blocked mage and the tank has 10 seconds to walk in and pick up Hydross . The drawback is that this uses the cooldowns on both Invisibility and Ice Block . Switching Form . Due to the stacking debuff , the damage taken by the tank sooner or later reaches levels where he simply gets one - shotted . Usually 100 % damage increase is the limit , in water form this means 22k crits are possible . Thus after 60 seconds ( = four debuffs ) , it ' s time for the current tank to move backward and pull Hydross over the boundary . This is a most critical moment , because immediately after a form switch Hydross resets his aggro list and summons four adds . There must be no DoTs on him and all DPS and healing must stop for a few seconds to give the tanks time to gain control of Hydross and the adds . If some raid member on the wrong side of the boundary draws aggro so that Hydross moves back over the boundary , he switches form again and summons four more adds ( = wipe ) . In water form he should be tanked at his initial position . There ' s a step running in front of his initial position , which forms an angle . Just down the step near that angle is a good tanking position for the poison form . Elemental Adds . Quickly killing the four elemental adds is a key to success in this fight . Good tanking coupled with solid AoE damage is the fastest solution , particularly if the AoE also includes Hydross . The optimal approach to this would be two Paladin tanks , one in Nature and one in Frost resistance gear . Unfortunately raids will rarely ever boast this luxury , therefore most groups will have to find their own solutions to the problem . Druid tanks work well , some combination of AoE and emergency " point " tanking by warriors does the job too . Resist gear is also useful on the add tanks . The faster the adds are killed , the less damage they do ( since their damage is increased by the raid - wide debuff too ) . Quotes . Aggro : Nature phase : Frost phase Killing a player in Water form : Killing a player in Poison form : Death in Water form : Death in Poison form :