How edited does a texture have to be legally distributed? I don't think I worded that right but my description will fill in the gaps.

In my case, I'm using a modders resource for a creature. The modder cleverly uses some of Dawngaurds assets. How much editing will I have to do before I can use it in my mod without adding 'requires dawngaurd'(although it doesn't really require it, it just requires you own the DLC)? I've already removed 33-40% of the texture and left it empty(uneeded portion) and changed the saturation, brightness and hue level. Is that enough?

Does the original mod/resource say "requires dawnguard"?

I think you're okay, but it's basically a question of whether your work could be confused for a specific asset of Bethesda's. So if it looks pretty much like the original, you need to make more changes. If it doesn't, you should be fine. Have you changed the model as well as the texture?

Pictures would be helpful, if you don't mind giving them out.

edit: grammar.