In Baldur's Gate 3, Aunt Ethel is one of the antagonists you encounter in various acts, and completing her quest line yields various rewards. Certain NPCs related to Ethel's quest can be freed after defeating the witch, so here is a complete walkthrough of the Overgrown Tunnel in BG3.
Aunt Ethel Complete Quest Line: Save Mayrina & Help Mayrina | Baldur's Gate 3 (BG3)
The Overgrown Tunnel is a secret passage in the Gnarled Teahouse. The Riverside Teahouse Waypoint is the closest fast travel point to Ethel's Teahouse. This is where you first encounter Auntie Ethel in her witch form.
You'll also find Mayrina here, and you can inform her of Ethel's true intentions. She killed Mayrina's brothers and plans to take Mayrina's child to get a new witch's body. Ethel also promised Mayrina that she would resurrect her dead husband (in a zombie form), so you'll have to make a decision regarding Connor towards the end of this quest.
After informing Mayrina about her brothers, Ethel banishes her to a magical prison, and a fight ensues between the witch and your party. Defeating Ethel at the Gnarled Teahouse isn't the end of it, as this character returns in Act III, where you must rescue Vanra, a child Ethel kidnaps for the same purpose.
