Since the TRS-80 had such low-resolution graphics, and with its pixels being about half as wide as they are tall, it was fairly challenging to come up with great visual designs for creatures to populate the dungeon. I drew many of the designs, plus a whole bunch that were never used. My younger brother Tim designed a lot of creatures as well.
We drew a lot of designs on quad paper, putting two pixels side-by-side into each square. Eventually I created a little graphics editor program for drawing, that I called GREDIT. If we had an idea for a monster such as a skeleton or troll, we would try to come up with a drawing that looked good. Sometimes we would instead start by doodling, and occasionally we ended up with something that looked visually interesting. Then we would have to invent a type of monster to suit our drawing. Each monster was drawn as a two-frame animation with a primary and secondary view, and the program animated between them.
In the end, we ended up with fifty-four different monsters, from Goblins to Greater Dragons.