When players reach Moonrise Towers in Act 2 of Baldur's Gate 3, they can use the opportunity to learn more about the source of Ketheric Thorm's immortality. In fact, Thorm's private quarters hold a lot of useful information about the conspiracy he helps lead.
Baldur's Gate 3: How to Enter Ketheric Thorm's Private Rooms in Moonrise Towers
Ketheric Thorm's chambers are locked tight and closely watched, but smart players can find several ways to sneak in.