So i have planned to have my party be attacked by a Defel assassin as in the back of the core rule book but im still trying to piece together exactly how it should be discribed. When it naturally bends light is it creating a "ripplely" dark shadow? Is it completely out of sight to the necked eye? Either way it would still be visible in infrared and ultraviolet lightwaves?

He adds 2 boost die to stealth checks while in the dark. But 3 setback while exposed to bright light. He is perfectly visible at infared and uv systems

The Defel is (at least according to the old West End Games system, where it first appeared) visible in the ultraviolet specturm of light. When viewed this way, they're actually quite colourful. However, to normal light they appear as two-dimensional shadows on whatever background they happen to stand in front of. The Defel doesn't bend light, their fur completely absorbs all light in the visible spectrum.

They also carry special goggles to help filter out blinding (to them) light, so the penalty would only be applied to a Defel who'd lost his goggles.

My suggestion would be to have the Defel pick the location of his fight with your players. He'd select a spot with lots of dark shadows, adding even more setback dice to attacks against him as well as checks to notice him at all. Remember that his two Boost dice stack with any additional Boost dice for sneaking around in the dark.

The defel assasin is quite deadly. Had a climatic battle with one and a wounded party on darkened space station, very predator-esque huning of the party. Sadly the group didn't have any survivors.

Actually the Defel originate from the Thrawn trilogy, which is a good series you should read it anyway. But they originally appear in "Dark Force Rising" right at the beginning. The first mention of the name is in Chapter 2.

Actually the Defel originate from the Thrawn trilogy, which is a good series you should read it anyway. But they originally appear in "Dark Force Rising" right at the beginning. The first mention of the name is in Chapter 2.

Nope. Galaxy Guide 4, first printing, 1989 had them. The Thrawn Trilogy was released starting in 1991.

Kallabecca is correct with that info.

OK, fair enough. Still a good resource for telling how to describe the effects.