I'm running a mixed party campaign at the moment, two of the characters are Force sensitives and one character is a droid technician. I plan to have the party track down a crystal cave soon so that the Force sensitives can get their hands on lightsaber crystals.

When they're in the caves the Force sensitives will be coming up against visions and tests, the Force reflecting inner conflicts etc. But as a droid with no connection to the Force the third character can't take part in that. What can I do to still challenge the droid and make the scenario interesting?

Combat droid? Perhaps the caves are a lair for dangerous animals - droid has to protect the meat bags while they're incapacitated by their visions.

Protocol droid? Perhaps a tribe sees the caves as sacred and must be distracted while the meat bags do their hallucination thing.

Mech droid? Perhaps the caves are unstable and only some ancient machinery prevents the tunnels being flooded by lava. Droid has to run around fixing stuff, it's unfamiliar with.

Mix in a bunch of hazards for added chaos / fun.

Alternatively, keep the droid player acting within the vision - the player isn't actually playing his droid, he's playing the meat bag's memory of the droid.

Or, a little evil, give him the stats for a "Force Wraith" with Misdirect and tell him he'll get bonus XP for tricking the other PCs into gaining Conflict.

Conspire with the droid player. Have him "killed" by something in the cave. If you're sneaky and lucky (mainly lucky) you will fool the other PCs into thinking you've actually killed his PC. Maybe the will lash out against who/whatever did it. A teaching moment for the force sensitives. Then they come out of the vision and the droid can be sitting around asking that the big deal is...