Here's another piece from that Necronomicon assignment. Pretty much exactly the same process here. For this one, I found that I'd saved my original sketch page, so I'll show you the painstaking procedure to get to the final drawing.
Well... not really. :) Actually I don't usually take a lot of time sketching unless I'm really stuck. I usually just try to imagine what's going to happen without drawing, which is quicker for me. Didn't used to be that way, but it's something I've developed over the years. (Years! Has it really been "years"? Wow...)
Idea sketches. Mostly just nailing down the unique anatomy for the creature. This is the "Gug", whom I'd never read about before. His double arms are interesting in that they break off at the elbow. I try to stay just loose and gestural in this phase so that I don't get "married" to any particular lines in the drawing. (15 mins including reading the brief.)

Final drawing. As you can see I based it on the final sketch from the previous page - I'd already had this pose in mind when I started. (20 mins)

Here I've added the median filter to the pencils to blob them up a bit, added a texture layer, and added a few of the initial light/dark values (using mostly dodge/burn. (10 mins)

Here I've skipped a few steps, but as with the Cthulhu piece I went into Painter and smudged it up, then back into Photoshop for detailing. Most of the details are done just with a simple round brush, though there are a few random-ish texture bits that used a sponge-texture brush. (about 1 hour)

Here's the final. The main difference between this step and the last is that I've punched up a few highlights, and added one more texture layer on top (it's a photo of a concrete floor, desaturated and set to 20% multiply). (10 mins)

Well, this one wasn't much different from the last one, really. I'll do a color piece next time! Let me know what you think, as always!