For the past year or so, I've done nearly all of my sketches straight-to-pen. I didn't set out to; I think I just found the definiteness of using a pen far more satisfying than a pencil. I think it's benefited me in that it has forced me to commit to the lines I put down, but a downside may be that it limits your ability to explore alternative design directions. It may have been necessary for me though because I can easily fall into the bad habit of endlessly trying to revise a section to make it perfect. Nonetheless I'm gonna try to force myself to branch out into different mediums.
These sketches are some examples of straight-to-pen sketches I've done in the past month or so. Recently I've been focusing on trying to get organic poses that don't just look like posed action-figures. A bit ago I noticed that my figures were way too rigid and straight up and down, so since then, I've tried to apply all of the principles of figure drawing I know of to the best of my ability.
I've also been trying to apply what I know about facial anatomy to draw distinct faces that vary in proportion and structure. A big inspiration has been reading Inoue Takehiko's manga Real. I was amazed by how he's able to draw in aspects of the face that are almost always left out or ignored by artists and yet still be able to make his characters appealing.
Figure drawings and heads from imagination:
a study of Smaug concept art: