As a speedpaint I think this is an excellent example; shape, mood, tone and colour are all well represented. My only concerns are in terms of opacities on certain elements, such as the arm, cloak and possibly the background. I feel that these could benefit from a more full application of colour to give a feel of depth and weight that they seem to be missing. The background in particular feels slightly under-worked in the lower right, but this may just be through compositional choice. That aside, I still feel that it's a fantastic piece and well done. Good job!
In one word: powerful! Transmits a very calm yet strong sensation. Pretty amazing for 30 min of work which gives it a somewhat abstract look to it. Very nice composition and choice of warm and metalic color pallete but i have to agree with what Pencil-X-Paper said, that lack of opacity in the arm creates a somewhat strong contrast with the rest of the drawing that is not very pleasing to the eye. Other than that is a beautiful paiting. Keep up the good work! Can't wait to view more of your work and learn from your drawings so keep them comming!