After defeating Jochi, head outside and find Sihek southwest of Kurast. Talk to him and he will take you to a home in the southeast corner of the city. Talk to him there, then go into the home to find and kill the infected Rakuni Scout.
Talk to Sihek again and he will ask you to get 10 Insect Shells from the Tormented Lacuni.
Head directly southeast of Kurast to find them, and kill them until you’ve gathered enough. Afterwards, look for a small camp to the west and examine the shiny object before returning to Sihek.
He is located near the entrance to the Undercity and talking to him will unlock the cave area. Examine the brazier and start another run to reach the cave area.
Reach the end and kill the Rakuni leader Longtusk to complete the mission.
Return to the entrance to the Undercity dungeon and Sihek will leave. Examine the tablet he left behind, then head to the council chambers northeast of Kurast to meet him and speak to Ormus.
Afterward, speak to Sihek again to unlock the full potential of Undercity and receive three “tributes” that can be used to add modifiers (and increase rewards) to your Undercity run. They can be found in the “Dungeon Keys” tab of the character sheet.
With all of this done, you’re now ready to tackle the random boss at the end of Undercity. These runs will help prepare you for the more challenging endgame events, so stick with it!
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