Crystalfang valley is the middle valley of Catian. To the south is Greenspring; to the northwest is Blacklake valley, and to the northeast is Greywind valley. It also borders Arthen to the southwest (though this piece of border is quite small), Brantleburg to the east (also a small border - though Brantleburg is a small kingdom), and North Dalwinland to the southeast.
The valley is named after Crystalfang Cave, which was once a marvel of natural geo-magical energies, and home to a particularly vicious and territorial yellow dragon. These days, it's just a hole in the ground, filled with abandoned mining equipment and probably a tribe of kobolds or two. Kobolds happen; it's just a fact of life.
With the mine no longer in operation, trade and travel have become the main industries of Crystalfang; it sits across the most convenient routes between Catian's other valleys, and also sees much of Brantleburg's trade output. Adventurers are not uncommon; the locals like to spread rumors of one last crystal in the cave - too large to move, or too small to have been worth excavating at the time, or stolen by kobolds for use in their shrines, or... the list goes on.
There is also, nestled in the southwestern corner of the valley, an old ruined chunk of castle. The locals try to send adventurers there, too, claiming that, once upon a time, it flew - and that no-one has ever figured out how, or found the power source that allowed it to do so. The adventurers, for their part, report crumbling masonry, dusty halls with intruding tree roots, perfectly ordinary sized spiders, and a general lack of anything even as interesting as kobolds.