ToME: the Tales of Maj'Eyal

Don't get me wrong, I love Illuminate.

However the following monster types should probably be immune to blindness based on their native environment or physiology; molds, slimes, jellies, oozes, worms, and snakes. All of these creatures either are generated primarily underground where there is no light and therefore would not have light sensing organs to be blinded or are based on real world creatures that rely heavily on vibration sensitivity.

If felines are ever added as a monster type they should probably be immune as well (a cats conal earshape allows it to pinpoint sounds with great accuracy).

Another solution would be to give these creature types the heightened senses talent. So they're still 'blinded' but it doesn't matter so much. (I think that works anyhow, I blinded an orc assassin and he didn't seem to care at all, but maybe it was just the RNG hating on me).

Are certain other creatures like non-uruk-hai orcs light sensitive? If they're not already that would also be fun. It would make the spell a bit more interesting perhaps.

Done

They are, in fact many of the creatures on this list are. Many undead are as well I believe and they're universally immune to blindness.

It doesn't seem to affect blindness saves though but rather damage from light (Sun Paladins do a lot of this) or would if negative resists were in place.

I also can see a creature taking extra damage from light and still being immune to blindness caused by illuminate. For instance it makes sense for a jelly that's lived with no light it's whole life to sense vibrations or heat signatures rather then see with light sensing organs to be immune to blindness and take extra damage from light.

I think giving heightened senses to such creatures is probably the best option.

Maybe if more immunities were put in place some light damage could be attached to Illuminate (not a lot but a little, enough to make it a good offense against light sensitive creatures but not really great as an offense against other actors.).

Edge, that list bit is exactly what I was thinking. It would be fun even if not perhaps that important if light sensitive creatures took a bit of damage from illuminate. I just couldn't remember if they did!

And not all undeads are immune to blindness right now, there are a few uniques that slipped through (like the shade )

Shades are pretty much always light vulnerable in almost all fantasy settings. I mean the Name pretty much says it all.