I think most of those effects use glow maps, which glow, but don't give off light (cause, yknow, that's totally possible in reality
![Razz :P](http://gamesas.com/images/smilies/icon_razz.gif)
).
Until the OP specifies if they want the creature to actually light up stuff around them (glow maps won't, lights will), not sure how much help anyone can be.