He previously worked for Maven Black-Briar, but, during a job transporting the Quill of Gemination across Lake Honrich, he crashed the boat and lost the quill. Since then, he's been in debt to Maven and worked as a guard watching over Riftweald Manor, owned by Mercer Frey.
Vald also used to have a close relationship with Vex.
During the quest the Dragonborn must infiltrate Mercer Frey's house; however, Vald is keeping guard of it. In doing so, Vald will become hostile and must be killed to gain entry.
However, if the Dragonborn speaks to Vex, she informs the Dragonborn that Vald only cares about money and that erasing his debts with Maven Black-Briar would gain his good side. If the Dragonborn speaks to Maven Black-Briar and asks to have his debt erased, then she will ask the Dragonborn to find the lost Quill of Gemination, which is locked in a strongbox in the wreckage of Vald's ship in Lake Honrich. If you cant talk to him (you need to show him his debt is gone) because he is attacking you, you can use spells like Calm or scrolls like Scroll of Harmony to make him stop attacking you.
Upon retrieving the quill and returning it to Maven, she will erase Vald's debt. Informing Vald that his debt is erased will result in him happily allowing the Dragonborn into Mercer's house before leaving Riften. If you cant talk to him, (you need to show him his debt is gone) because he is attacking you, you can use spells like Calm or scrolls like Scroll of Harmony to make him stop attacking you.
- If you try to pickpocket the key from Vald and are detected, you will not be able to talk to him after giving Maven the Quill. Even paying off any accrued bounty will not make it possible to talk to him. Dual casting an Illusion spell (such as Calm) with the relevant perks may be the only way to make this possible.