You go to the Ascension Forge next to all the R8 forges.
It tells you what mats you need.
A combination of 200-300st and 5-10 SoWs,
depending on cape type.
Supreme > Ascended Supreme
Dragon > Ascended Dragon
Or the lunar capes, if you so choose.
That's it.
Unless you mean the unascended versions, first.
