In order to get a good post in this week I'm posting this one in very rough form with an outline that kind of shows the process of how I think about generating the stats and abilities for a new beastie.
Gnomes are kind-hearted, family oriented illusionists, goblins are chaotic little murder machines who hate the light. Common theme: both dwell in the underground and are diminutive in size.
HD 1/2 to 2
AC 13 to 16
Atk 1 weapon (1d6)
Save 18 to 13
Special: -1 to hit in sunlight.
Illusion spells levels 1-3 (define spell list).
A gnomblin has magical ability equivalent to double its hit dice. Gnomblins save vs. magic or wands with a +4 bonus. It is theoretically possible for individuals of even greater power to exist. The Game Master can roll spells randomly or determine appropriate choices from the Magic-User spell list.
I've been developing this idea of goblins being fecund; willing to breed with anything and everything. Because of their unique DNA they are able to create offspring, mostly sterile, with almost any humanoid. This opens up no end of options for interesting little goblin+ hybrids. I've been having a lot of fun drawing these little beasties, and hope you are enjoying them too, I have several more in the pipeline. Also the Gnome/Goblin war of 576 which I have a LOT more to say about in the future.