This is my attempt at creating a Pontiff Sulyvahn robe. I'm still very new to modifying textures so it turned out pretty rough around the edges, however it gets the general idea across. I did this by changing some of the colours, changing the pattern in some areas, and adding transparent tears wherever I could. Unfortunately, I couldn't make some areas of the robe transparent (particularly the shoulders and the mini-cape at the back) so if anybody wants to give it a shot please do.

This mod (and ALL texture mods for Dark Souls 3) requires the use of IGP11 in order to allow the dumping and swapping of texture files:
https://www.nexusmods.com/darksouls3/mods/28/

Follow the IGP11 installation instructions and once complete extract all files from the pontiff folder into your tex_override folder. BOOM, that's it.

Make sure to run Dark Souls 3 from IGP11 to enable texture mods or you won't see any difference.

Some Issues with the texture:
-Can be too bright in some areas
-Clipping with Great Swords in right hand
-Seam on the neck
-Some of the tearing is sloppy

Overall this turned out pretty sloppy. I'm sure somebody with experience could accomplish what I was attempting here with much ease. Regardless, I hope you enjoy.

Outfit worn is:
-Giants Crown
-Court Sorcerer's Robe
-Giants Bracers
-Giants Leggings

Giants set is added by this mod https://www.nexusmods.com/darksouls3/mods/293 made by KepaszX. It's pretty cool and I recommend it if you have any interest in the unused armor from Dark Souls 3.