You must obtain written permission from the proper and legal owner of any work which you wish to use, credit alone does not replace this requirement. Failure to obtain proper permission for the use of works protected under copyright can leave your deviantART submission vulnerable to being removed following a claim of infringement against it.
Explicit permission is not required when you choose to use valid stock resources. Please check your sources carefully to ensure that they are valid stock and please be certain to obey all rules, terms and conditions which may be attached to that resource.
Except i have no idea who the author is. I've reverse image searched it and couldn't find anything besides reposts. Even so, I'm pretty sure this talks about using other people's actual art, like I did with MagicnaAnavi and her witchblade art.