From Diablo Wiki
Trigger: Enter Sardar's Tomb
Completion Details: Find the treasure of Sardar.
This event will occasionally spawn in the northern portion of the Dahlgur Oasis. There will be a raised section with a lever on top, and once the player interacts with the lever, a stone will will drop below, revealing the entrance to Sardar's Tomb.
Entering the tomb will initiate the event. The player is first tasked with finding another lever within the dungeon, as the door guarding Sardar's treasure is locked by this mechanism. The dungeon is similar in look and layout to the sewers in Act II, but it isn't nearly as large or labrynthine as the sewer dungeons. The lever will spawn randomly in the north, east, south, or west corners of the map.
The dungeon is filled mostly with Betrayed (an alternate type of Accursed demon), and they can be quite deadly due to the narrow corridors and leaving behind a poison cloud after they die. They are accompanied by other lesser monsters, but the Betrayed remain the main threat. It is normal to have one to two elite packs spawn in this dungeon, and they are normally Betrayed.
The lever needed to open the door to the treasure vault will be placed randomly in one of the corners of the map. The most efficient route is to pick a side upon entering the dungeon and explore it to the very end, then backtracking and finishing up the rest of the side before moving on.
Once in the treasure vault, Sardar's treasure will be placed in a unique-looking chest in the center. Opening it will spawn the treasure, and also Sardar himself.
The damage modifiers he possesses are Plagued which lays down pools of poison that inflict damage but also applies a debuff that reduces the armor of Barbarians and Monks by 50%, and causes the Witch Doctor, Wizard, and Demon Hunter to take Reflected Damage.
He also has Nightmarish which is basically 'fear', making the player run away during which period they have no control over movement.
He comes with very few minions and if you avoid his pools of Plague he's a quick fight.
Killing Sardar finishes the event.
A video of the event:
|Quests & Events of Diablo III  Act I Act II Act III & Act IV Act V|
|Act II Quests||Act II Events |
|Quests Act III||Events Act III||Quests Act IV |