Paid in Full

Walkthrough
Should the Dragonborn be member of the Thieves' Guild, a dialogue option will come up to remark on the Shadowmark near the door of Glover Mallory's House. As it turns out Glover Mallory is member of the guild, their representative here on Solstheim, and the brother of Delvin Mallory. Further inquiry reveals that recently a thief named Esmond Tyna, embarrassingly, stole a valuable Bonemold Formula and fled to the Castle Karstaag Ruins.

Recover the Bonemold Formula for Glover Mallory
The Dragonborn offers to help, travelling to the Castle Karstaag Caverns, where near the lower entrance on an ice shelf the body of Esmond Tyna can be found, and the formula as well.

Bring the Bonemold Formula to Glover Mallory
Return to Glover Mallory with the Bonemold Formula and receive an slightly unusual reward, not only Glover Mallory's House Key but also Glover's Guild Key. The latter opens up the guild's treasure room located in the cellar of Glover Mallory's House.

Epilogue
Looking through the loot in the cellar, the Dragonborn may notice Glover's Letter. Reading it uncovers that Sapphire another member of the Thieves' Guild over in Riften is actually Glover's daughter. Taking the letter to Sapphire makes her very happy and yields a unique and very valuable Exquisite Sapphire worth 5000.

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