Background
The walls of The Keep of Vigil seems damaged. Voldrik asks you to help him re-building them. (needs edit)
Walkthrough
There are two ways to do it:
a) You pay him 80 gold
b) You tell him to make from what there is available, then he asks to find Granite Deposit which is located (on red circle):
(Note) Even if you do pay him 80 gold, he will still ask for you to find Granite anyway
Result
XP & Gold