Ouro

The ancient sand worm, Ouro, is a being of legendary power. He is rumored to have been created by the Old God C'Thun himself as a mockery of life. He resides in the Temple of Ahn'Qiraj.

His skin is unnaturally thick, nearly impregnable. It's flexible and allows him to move with the speed and grace of a much smaller creature.

Phase One

 * Abilities
 * Sweep: 1k-2.5k physical damage (with AoE knockback, often result in temporary switch aggro to ranged group and sandblast ranged group). Keep in mind, usually after a sweep, a tank will lose aggro and a new tank will be on Ouro's aggro list. It is crucial that the tank who was swept not go in melee range, as Ouro will return to that warrior, and chances are that warrior will not be full health.
 * Sand Blast: 3.5k - 4.5k nature damage. Frontal breath affecting 180 degrees. You can fully resist it or not, damage is not reduced/blocked because it has an incapacitating effect that makes it a binary spell. Ouro sandblasts in the direction of the person in the raid with the highest threat and being hit by the sandblast clears all threat for that person. Sand Blast is every 20–25 seconds. It has 45 yards range and can be easily outranged.
 * Submerge - Burrows under the ground. Ouro becomes untargettable and undamagable. Ouro has a chance to submerge every 1.5minutes. He will not submerge if he is busy casting a Sand Blast or Sweep, else he will submerge (ie. the chance of submerging is totally random). It will also submerge if no player is in melee range of it.
 * Ground Rupture - 2k physical damage to anyone on top of Ouro when it reappears from a submerge.
 * Dirt Mound's Quake: With 200 NR, expect 1000 nature damage, with around 500 resisted. This is done when Ouro is submerged.
 * Scarabs: They hit for 300 on cloth, 40-150 on tanks. They will pick an initial target and will never change targets. They will despawn on their own after 45 seconds.

Ouro seems to give you about 10 seconds to get a MT in there when he pops up, otherwise he goes right back down. In order to determine where he will surface, it is advised that everyone in the raid stay near the center area (or predetermined area) near the end of the submerging phase. Once he appears, have multiple tanks on Ouro, to ensure he does not submerge again. Regardless of any deaths, Ouro will resurface with scarabs, they will despawn after 45 seconds so fears, frost nova, frost traps, and any forms of CC is adequate.

Usually he starts with a frontal cone of Sand Blast after popping up. It does not happen immediately so there is time for positioning shorting after resurfacing. Try to avoid that if you are not the MT. Don't stay over the Dirt Mound, as it hits multiple times (in fact, usually it hits until you die).

The raid should be positioned using 3 groups spread with 120º between them. Healers at the back away so they don't suffer Sand Blast. Sand Blast does up to 4.6k damage. It is a matter of having enough health and let the healers top your hp after each hit.

Usually you get out of combat for a second each time Ouro is about to go up. If you spam the button, you can drink.

Phase Two
At 20%, Ouro gains enrage, +150% attack speed, + 100% attack damage. From this point on, Ouro will not submerge again, but he summons Dirt Mound Quakes and Scarabs while remaining up. DPS is much more important than NR in this stage, you need kill it ASAP, and at 20% he has about 400,000 health.

If no one is in melee range during this phase, he will throw boulders for ~6000 damages to a raid member, pretty much like in the Ragnaros encounter.

Loot

 * He does drop a single Qiraji Lord's Insignia.

Trivia

 * Ouro's name is almost certainly a nod to Ouroboros, the ancient symbol of a dragon eating its own tail, representing cyclicality.
 * Ouro was the longest ever unkilled boss in vanilla World of Warcraft, 86 days after the first Twin Emperors kill, with C'Thun and Onyxia just behind him. This is because he was very bugged at release, and he was an optional boss.