The Obsidian Sanctum is the black dragonflight area of the Chamber of Aspects. The entrance is in Dragonblight [59.3, 49.3] and accessed via a crack in the ice below Wyrmrest Temple. It holds one raid boss, Sartharion the Onyx Guardian, and his three drake lieutenants, Shadron, Tenebron, and Vesperon. Raiders may choose to kill all three drakes or leave some combination of them alive. Completing the encounter with one or more drakes up increases both the difficulty and the quality of loot that drops.
Will of Sartharion - Sartharion's presence bolsters the resolve of the Twilight Drakes, increasing their total health by 25%. This effect also increases Sartharion's health by 25%. Active only while fighting Sartharion with drakes alive.
This will give each drake 1,220,187 health in 10 player (2,789,000 in 25 player) and Sartharion 3,137,625 health in 10 player (9,597,500 in 25 player) respectively.
Power of Tenebron - Tenebron's presence increases shadow damage taken by 100%. Active only while fighting Sartharion.
Lands 30 seconds into the encounter, if left alive.
Tenebron's portal spawns eggs which hatch into whelp adds.
Power of Shadron - Shadron's presence increases fire damage taken increased by 100%. Active only while fighting Sartharion.
Lands 75 seconds into the encounter, if left alive.
Shadron's portal contains a disciple who increases Fire damage done by Sartharion by 50% and makes Sartharion immune to damage. (If engaging Shadron alone, instead the disciple increases Shadow damage done by Shadron by 50% and makes Shadron immune to damage.)
Power of Vesperon - Vesperon's presence decreases maximum health by 25%. Active only while fighting Sartharion.
Lands 120 seconds into the encounter, if left alive.
Vesperon's portal contains a disciple who increases Fire and Shadow damage taken by 75% and puts Twilight Torment on the raid, making them damage themselves when attacking.
Shared Drake Abilities
Each drake can be taken down without engaging Sartharion. The achievements require leaving one, two, or all three of them up. If you kill them before engaging the primary boss, they each drop an [Emblem of Triumph] but no other loot.
Shadow Breath - 10-man, 25-man Fairly substantial frontal shadow damage. Should only ever hit the drake's tank. Not a major issue if the drakes are alone, but Power of Tenebron and Gift of Twilight (see Shadron's section) can make it hit considerably harder. Cast every 20 or so seconds.
Shadow Fissure - 10-man, 25-man Identical to Kel'thuzad's although less damaging. Creates a shadowy area on the ground which hits everyone within it for a large amount of shadow damage after five seconds. Not fatal if the drake is alone, but again, Power of Tenebron / Gift of Twilight will make it one-shot non tanks.
Twilight Revenge - Sartharion's attacks become increasingly frenzied as twilight drakes are killed, increasing Physical damage and attack speed by 25%. Stacks up to 3 times. Is not applied if drakes are killed prior to engaging Sartharion.
Vesperon and Shadron
Each drake fight is a typical tank and spank, but after 15-20s the drake will open a portal. One healer, one off tank, and all dps need to take the portal, leaving only the main tank and his healer behind. Much like phased content, you'll be in the same place (totems still exist where you left them), but instead of seeing the drake, you'll fight a disciple of whichever drake it is. They have a shadow aura that reduces damage taken by 25%, but periodically pulses shadow damage to you.
Vesperon's disciple will place Twilight Torment (http://www.wowhead.com/?spell=58835) on the raid frequently, which increases fire and shadow damage taken by 75% and causes you to deal damage to yourself on hit. It used to be possible to temporarily remove the Twilight Torment debuff with any damage other than autoattacking, but the ability was changed with patch 3.0.8 and this is not possible anymore. This disciple can be ignored if fighting Vesperon alone, but is extremely dangerous in a multi-drake Sartharion fight.
Shadron's disciple will place Gift of Twilight (http://www.wowhead.com/?spell=57835) on Shadron which increases all Shadow damage done by 50% and provides complete immunity to damage. If fighting Sartharion with Shadron alive, the disciple will use a different version of Gift of Twilight (http://www.wowhead.com/?spell=58766) and buff Sartharion instead, increasing Fire damage done by 50% and provides complete immunity to damage. This can and will buff Sartharion's Flame Breath to levels that will one-shot your tank if left unmitigated in combination with Power of Shadron, Twilight Torment, and so on. Shadron alone with this buff is not terribly threatening, although his Shadow Fissures can one-shot low HP targets while Gift of Twilight is active.
Tenebron is similar to the first two drakes, except that in the alternate realm, instead of a disciple, you will encounter several eggs. The portal group will need to kill as many eggs as possible before reaching a time limit, at which point the eggs hatch, and everyone is reverted to the real world. Any unkilled eggs spawn whelps, which must be tanked and killed as quickly as possible, so that the DPS can return to the drake before the next portal appears. Each of the whelps can apply a stacking Fade Armor debuff, reducing armor by about 1200.
Most groups will find it is easier to ignore Tenebron's portals and tank/AOE his whelps down, as the dps loss from taking the portal will typically compensate for the higher health of the whelps as compared to their eggs.
For Sartharion + one drake learning purposes, Sartharion + Tenebron is probably the easiest step up, since you have the option of just burning the drake and off-tanking/AOE'ing the whelps without taking the portal. With the others, you either take the portal and waste a bunch of time, or don't take the portal and eat a nasty debuff for a while.
When attempting 2 drakes and up, make sure that after killing Tenebron and before taking on the next drake that all whelp add's are killed, as whelps can cross realms between the playing field and the void zone, and can cause a wipe if the tank goes through the portal before all whelps are dead, as they will rampage and go after healers and DPS that AoE them.
Cleave - Inflicts 35% weapon damage to an enemy and its nearest allies, affecting up to 10 targets.
Tail Lash - A sweeping tail strike hits all enemies behind the caster, inflicting 3063 to 3937 (4375 to 5625 Heroic) damage and stunning them for 2 sec.
Fire Breath - Inflicts 8750 to 11250 (10938 to 14062 Heroic) Fire damage to enemies in a cone in front of the caster.
Will cast Pyrobuffet at anyone outside the area of his platform, rapidly killing them. Brief dips in the lava will generally not trigger Pyrobuffet.
Sartharion has a 15-minute enrage timer, at which time he will spam Pyrobuffets regardless of location.
His immediate area is surrounded by a small moat of lava. The north (right) / south (left) sides of this lava spawn lava waves by Sartharion during his emotes every 30 seconds. See layout/positioning images below for details. Everyone must stay in the layout to prevent the Pyrobuffet.
Despite his cleave being rather weak, it can still deal a lot of damage to cloth and leather wearers so it is generally best for players to treat the cleave as deadly as the raid will be taking AOE damage from adds and other effects during the encounter, this will reduce the amount of healing stress on your healers greatly.
At certain intervals, a raid warning will appear saying, "The lava surrounding Sartharion churns!" Lava waves will then spawn that originate from the left or right of the encounter area. These waves place a DoT on any players caught in them, so players should move to the gaps between them. The location of the gaps is predictable depending on the side that the waves originate from, as shown in the illustrations. They are huge, obvious, and slow-moving, however, so players should have no trouble watching for them and moving out of their way.
When the wave originates from the left, the tank will need to rotate Satharion away from the group to avoid the wave, as shown. When the wave originates from the right, the tank should not have to move. At all times players should avoid Satharion's cleave, breath, and tail swipe.
It is possible to heal the tank through the lava waves and resulting DoT, if your group desires so.
Sartharion's Fire elemental Adds
Health: 65165 (25), ~26,000 (10)
These adds are summoned every ?s in groups of 2-4 to be offtanked. If these adds are hit by the lava waves they will enrage to deal 400% more damage, so ~800 becomes 4k, modified by Shadron's aura. Adds should be moved out of the path of the Lava Strikes. DPS will have to drop these as priority after they spawn and are picked up by the OT. The offtank must be careful using area of effect taunts when gathering the adds because Sartharion is not immune to taunt. Rogues can use Fan of Knives with Anesthetic Poison and Hunters can use Tranquilizing Shot to dispel the enrage from the adds, greatly reducing both the damage they inflict and the DPS needed to eliminate them.
The major drake of issue is Shadron since everything in the encounter is fire damage. Vesperon is less an issue as your raid is better geared. First time groups should take down all 3 drakes, making the encounter a tank and spank, minor add control, and minor movement to avoid waves. Subsequent visits may provide the chance to try while leaving Tenebron/Vesperon up.
At 10% he goes into a sort of soft enrage, summoning what looks like 5-10 of the elemental adds.
Lava elemental add's do not cross over into void zones when you go into them, but whelps do.
Engaging With Drakes Still Alive
When clearing the instance with the intention of leaving one, two, or all three drakes alive all trash must still be cleared before engaging Sartharion. It is possible to clear trash without grabbing aggro from the drakes simply by moving along the wall far behind them. All trash and the drakes are linked with Sartharion.
When engaging Sartharion with drakes left alive, they will join in the fight as if you were encountering normally: they will melee whoever is tanking them, cast the Kael'thas-like Flamestrike, and create portals for adds. Needless to say, the fight takes a huge jump in difficulty as not only do you have to pay attention to the elemental adds and waves around the area, but now you have to simultaneously deal with drakes and clearing their adds. The drakes, upon engaging Sartharion, can and should all be killed first. At the start of the fight, they will hover overhead and apply their respective aura then come down at their respective times and start attacking and summoning portals.
The offtank should remember that the drakes do a frontal cone shadow breath and to keep them faced away from the raid, preferably parallel with how the main tank is turning Sartharion to make avoiding waves easier. If there's a good supply of rogues and hunters, misdirects can be used to bring fire adds over towards the offtank to give ample time for taunts and aggro upkeep. If this is too much trouble, a third offtank should handle the fire adds and pile them near the drake so AoE can be at its most effective.
A subgroup of a healer and DPS (the less needed to eliminate a disciple or eggs, the better) should focus on going into the portals and taking care of the adds drakes spawn. At a certain level of gear, almost anyone is able to tank a disciple but will take amplified shadow damage from Tenebron's aura.
Normal Difficulty Composition
It is highly recommended that every raider is Tier 7 / Heroic geared before trying Sartharion with any drakes up as the urgency of killing adds will require a high DPS output.
1 Main Tank
1-2 offtanks for drakes / fire adds
1-2 AoE healers + 1 Holy Paladin
2+ AoE DPS ( Death Knight, Retribution Paladin, Fury/Arms warrior, Mage, Warlock, Hunter, Balance Druid)
2-3 DPS/CC (Rogue, Mage, Hunter)
Zerg Strategy with Drakes up
A group with high enough DPS can attempt to take down Sartharion before two drakes land.
Typically on 10, 8 dps, a tank and a healer are used. The drakes do however, enrage once Sartharion gets to low health, so an offtank, or class capable of kiting may try to move Tenebron away from Sartharion, as the damage may be too much for the tank to handle. Tenebron is the first drake to come down. When Sartharion reaches 25% health, Tenebron will start hitting for 25 K shadow damage. Healing and tanking cooldowns should be used starting at this 25% health mark. The ability to resist Tenebron's shadow attacks is unknown. With the normal 130 shadow resist aura, the roughly 32 K shadow attack was partially resisted, but always to the exact same number around 25 K. Resist all potions and/or flasks made no difference to the resisted amount, or the net amount of damage.
[info from http://www.wowwiki.com/Sartharion]
3 Drakes Alive
No Drakes Alive