After defeating Yoche, head outside and find Sihek in the southwestern part of Kurast. Speak to him and he’ll direct you to a home in the southeastern corner of the city. Speak to him there, then head inside the home to find and kill the Infected Lacuni Scout.
Speak to Sihek again and he’ll task you with obtaining 10 Insect Husks from Afflicted Lacuni.
Head directly southeast of Kurast to find them, then kill them until you’ve gathered a sufficient number. After that, seek out a small encampment to the west and inspect the shining objects, then return to Sihek.
He’s near the entrance to the Undercity, and speaking to him will unlock the Cave District. Inspect the brazier and start another run to reach the Cave District.
Reach the end and slay the Lacuni boss, Longtooth, to complete the quest.
Head back to the entrance to the Undercity dungeon and Sihek will have left. Inspect the tablet he left, then head to the council chambers in the northeastern section of Kurast to meet him and speak with Ormus.
After that, speak with Sihek again to unlock the full potential of the Undercity, as well as acquire three ‘Tributes,’ which can be used to add modifiers (and increase rewards) from Undercity runs. They can be found in the Dungeon Key tab of your character sheet.
With all of that done, you’re now ready to tackle the random bosses at the end of the Undercity. These runs will help you get geared up to tackle even more challenging endgame activities, so keep at it!
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