Alright, I'll bite.
Critiques are often aggressive so bear with me.
From the MTG art director instructions:
Color: Black, dark
Action: Item in golem's hand. Golem.
Focus: Walking golem with item.
I've circled some problem areas on the piece.
His shoulder needs some work. Take some photos of your shoulder or a friend's shoulder. If you need a model, tons of resources are available on modelmayhem.com if you want someone if that'll help. Musculature cannot be overlooked or given only a first pass.
The lighting on the quadricep needs some love. Where is the light source here? It's the artifact diamond, not a sun. (It's underground.) If you want to make an "underdark" type light, google them and see how masters have expertly captured only the necessary light.
The background red circles are what catch my eye but these things aren't defined, what are they? If they're out of focus, make them really out of focus. Photoshop filters should never be obvious.
I added lines for his weight shift. Try to recreate it. The head placement isn't possible. (Yes it's a golem, fine, but I don't think you intended for it to approach the uncanny valley
Finish the background.
Buy these two books now:
Imaginative Realism: How to Paint What Doesn't Exist by James Gurney
Color and Light: A Guide for the Ralist Painter by James Gurney
They'll help you with your lighting issues.
Make more and submit them for others to see constantly.
Visit conventions and meet with art directors.
Always include a link to a portfolio like DeviantArt or your website.
You're on your way.