What Lies Below

 is a quest in the Undermountain Campaign which takes adventurers to a new campaign zone, Twisted Caverns. This quest becomes available after completing both the previous quest, A Tribute Lost and Found, and finishing the second Undermountain campaign task Catacombs Depths.

Steps

 * Speak with Obaya Uday in the Yawning Portal 
 * Speak with Azuli Tefnek in Catacombs
 * Go to Undermountain Expedition
 * Complete the Expedition to Twisted Caverns
 * Talk to Azuli Tefnek
 * Talk to Azuli Tefnek