Sewers of Nihilia, Purifying Plant

Overview

This instance is reached by speaking with High Priest Diru Riwirn in Barindu as the first step in progression. If you have already completed it or wish to go for xp and random drops you can tell Gamesh "plant". The walkthrough below is for the progression version. For the Gamesh version you can simply do as you wish.

Mobs in the zone range from 61-65 hitting as high as 1100. In addition to the 3 loot dropping rares there are two zonewide drops Turepta Spine Ring and Earring of the Moon Dancer.

Start by clearing your way to Ansharu on the eastern side of the zone. Hail him and follow the dialog and he tells you the source of the problems with the stomemites is an alpha that lives deep in the plant. If you can kill it the stonemites should lose coordination and be easier to contain. To draw out the alpha you'll need to kill all of the 'an aged stonemite'.

Make your way to the far southwestern chamber and find 9 aged stonemites. These hit for 1200 and can AE rampage. Pull and kill them one at a time, but rest up before pulling the last one. When the final aged dies Ancient Kayserops spawns on the western side of the chamber. It hits for up to 1500, comes buffed with 65% haste, 250 attack, and 180 AC so a quick dispel is suggested. Procs an AE that drains 175 mana and deals 275 damage. Its death completes the expedition and gives a character flag.

Rare Mobs

Rare mobs do not spawn until you have killed at least 20 mobs. This is to prevent people from simply spawning instances over and over. All three rares drop Processing Gizmo for Breakdown in Communications quest.
Grimy Turepta
Rare turtle. Can hit as high as 1200 but pure melee.
Drops - Sodden Turepta Hide Wristbands, Smooth Gem of the Tides, Discordant Stone of Flame
Kril V'lak
Rare Noc. Can hit for 1300.
Drops - Tarnished Ringmail Sleeves, Veil of Mist, Wailing Coral Staff
Ukun Packleader
Rare Ukun. Hits for 1200.
Drops - Grimy Sandals of the Scribe Taelosian Meditation Beads Illuminated Gem of Concentration