Divine Ashes are one of those tricky crafting components that will start showing up for armor in and you will have no idea whether this is something you should have found by now but have somehow missed or whether this is just a way of the game holding you back so you don’t get too overpowered. Unfortunately, is probably the former in that you have missed it. Fear not, it is easy to find and you should be able to go get some right away.
In order to get Divine Ashes, you will need to travel to Musphelheim. In order to do that, you will need to have obtained the second part of the Musphelheim seed. Click the link <- back there for the guide on that if you have not found it yet. To save you the click, you will need to have the ability to break the rocks that have the orange cracks in them first.
Once you have it, travel to Musphelheim and take part in the crucible events there. For each event you complete, a gold chest will rise out of the ground and it will contain some Divine Ashes for you to use in your crafting. Use them sparingly now, as there is not an infinite amount of crucible events for you to take part in.