The Gurdian Picture

This another concept art character i did for concept art 2 class (before i failed that semester T.T) It's a greek warrior guarding a the entrance to Tartarus (In classic Greek mythology, below Heaven, Earth, and Pontus is Tartarus ) any way i need comments for my work , need to know where to improve , so comments and critique are welcome ,thank you .

(The muscle looks kind of weird , my be someday if i am free i will change it )
Persephone
The Horrible and Humilating Fate of the Titans
The Gurdian
Erebo
The Divine Three