In the past, I have allowed altered humans in the storyline. One was an escaped slave of the aboleth; his skin had been transformed into a slimy mucus and he could breathe underwater. The other character, an experiment of the sahuagin, had similar adaptations. As for my favorite character, that would be Xaetra, the night hag (now a spectral hag) protagonist who has been included in all of my online games since 1995. When it comes to the rules, I mix the 3e core rulebooks (DMG, PH, MM), a handful of d20 supplements (Seas of Blood, Seafarers Handbook, Broadsides), and a few rules from 2e and 1e. To this I add my fascination with the sea and information gleaned from the Discover Channel and similar sources.