Swamped

You decide it's best to do a search, which means you ought to put the rock back in place. First, though, you opt to do a quick test.

You grab a handful of sand. There seems to be a decent-sized pebble in it, so you stick with that and let the grains drop.

Then you toss it right at the crystal.

It bounces off harmlessly. The only thing you notice is that there's the slightest hint of a melody in the sound. It's like the sort of note you'd get from hitting a water glass.

The croc growls... oddly enough, at the crystal rather than you. Well, you don't think you want to bother it any more than you really need to. You move the rock back in place and hop on your desert horse.

Before you get to riding, though, you check your quickly-sketched map to see if your guides mentioned anything in the area.

Hmm... Closest thing you can see is the greblings' junkyard, but that's still at least ten minutes of riding from here. You suppose that doesn't rule it out as an option - perhaps Rider found himself another mount - but maybe there's something else. You're not sure where you'd start looking if there were, though.

How do you proceed from here?