This is what we call copypasta / art theft in the art community.
It's only OK to trace or copy a drawing of another's work when it's used purely for educational use, and should never be posted to make profit or otherwise take credit for the work. You may copy Master drawings for practice and sometimes for portfolio submissions to art schools, but that is it.
Otherwise, you may only use it as an inspirational reference that should not be a blatant copy and your work must be transformative
RE: Fire Dragon