[Quest] Price of peace

[Kamoteur]

Hi everyone!
I've been looking on google and this forum but i didn't found anything. I'm stuck at the begining of this quest. I have the reaver's ashes in my quest inventory, and i'm supposed to find and slayne silverwind but don't know where to find him or it. For information it is in the region of Ellyrionat at the Elthrai's Gates. When i go there i can click on the altar but not interact with it nor the ashes. If someone can help me it would be greatly appreciated.
Thanks!

[Captforbes]

Me too !

[Captforbes]

I finded the horse Silverwind not far of the trees. Kill it ! Drop the ashes in the altar.