Here's how to unlock the Underroot Dungeon in Diablo 4 and get Aspect of the Expectant.
Daughter of the Oak Diablo 4 Side Quest - D4
Diablo 4 Dungeons: Aspects & Locations (Season 3)
Underroot - Diablo 4 Guide - IGN
I Tested XP in All 130 Dungeons & Strongholds So You Don't Have To
Diablo 4 - All Side Quests Found In Dungeons - GameSpot
Diablo 4: All Dungeon Locations in Scosglen (& The Aspects They
Page 277 – PC Invasion
Diablo 4 Necromancer Dungeons: Aspects and Locations
Diablo 4 Underroot: Location, How to clear, rewards, and more
Page 452 – PC Invasion