If he's still walking around Silverglen and hasn't disappeared after declining his request., you can maybe try to mine tenebrium veins in the Troll King cave and then try him again. Declining this quest was a very unique role playing choice to make as you now have only one party member that can use this ability.
If that dosnt work your only option left is Lone Wolf. Enjoy!
Last edited by allsweptaway; 17/07/14 07:17 AM.