You can , i did that just a moment ago.
And for a fifth time The warden doesn't know how to become reaver and Kolgrim is his only mean to obtain reaver abilities ,how one can't understand so simple statement especially repeated 4 times?
Destroy urn full of ashes that have not proven to have any special properties by that point in return for magic power and avoiding very difficult and unnecessary fight? You would have to assume that The warden has them in your team during doing that and even if you have them you could hope to convince them what for 1 of them may work if you made proper choices.The only way to obtain reaver specialization in dao is cheating or save scumming needless to say it matters only gameplay wise not story wise.
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At the end of the day anyone is entitled to a personal opinion on the approach of the problem, still i believe that is useless to lose 2 party members and destroy the urn for something that can be obtained the same.
For the 20th time
Lore wise become a reaver is a silly thing the warden especially if from an educated background
(mage or human noble)should know that ,gameplay wise you are forced to rely on Kolgrim ,while i already said that in order to be a reaver simple dragon blood work better than Wyvern blood and it does not need prepararion you only need to take blood and drink nothing more .
You don't need to be a nobel prize scientist to read some book about dragons (and the human noble background gave hint that the warden of that origin often read books about dragons) discover that.
And the urn is far and it still remain for me far more valuable than common wyvern blood, those who opted differently evidently lost wynne, possibly leliana for nothing a spec that is always or unlocked (as it should have been from the start since it is not something that come from a teaching) or unlocked via tomes in DAA.
Ah did i mention that those morons who destroyed the urn didn't get the epilogue in which is stated that pelgrim all over the world come into ferelden to see it?
This is turism buisness for the nation after the blight, i doubt that a dirty wyvern blood is useful in the same way for the nation ,and before that you will start by saiyng that the deal with that mad man of Kolgrim is necessary to stop the blight no it is not necessary and neither make things more simple.