When looking for Andraste's Ashes, you'll travel through caves in the mountains and then face a man with a huge battleaxe and a few others. Don't kill them. They will offer you the chance to pour blood into Andraste's Ashes. Agree to do this and progress through the mountains and into the chamber with the ashes. Pick some ashes out first for yourself, and then pour the dragon's blood into the Ashes. The Guardian will fight you as you try to leave. Take care of him and proceed out. The man with the axe will be outside and will give you dragon's blood to drink, which will give you the Reaver specialization.
- IF LELIANA IS WITH YOU WHEN YOU DESTROY THE ASHES, SHE WILL PROBABLY TURN ON YOU AND LEAVE THE PARTY.***IF NOT, YOU WILL HAVE ONE CHANCE WHEN YOU RETURN TO CAMP TO PERSUADE HER THAT YOU DIDN'T POISON THE ASHES**
However, you can always take back that action. Save before you decide to side with Kolgrim and do the above, and when you have unlocked the Reaver specialization, you will have it permanently. So if you should decide NOT to poison Andraste's ashes you can just unlock the Reaver Spec and then reload the earlier save that took place prior to that event.