The Royal line is one of three bloodlines containing the Charter, along with the Abhorsen and the Clayr. Those of the royal line include the King or Queen (only one individual is designated as such at a time) and all relatives. Apparently, the royal line has berserker blood as well (which is why Ranna, the sleeper was born by Touchstone). All tend to be potent charter mages. Their symbol is a golden tower, and the color is red.
The Royal Line is a very short walk from parking that requires route finding. Park at the posted coordinates, then hike up the jeep road to the top. The road splits into a northbound and southbound road, but you will leave the road and continue east down the ridge to where it levels out. You are looking for a juniper tree that was destroyed by charter magic on the east side, and there is a fallen juniper that you can use as a seat when you get there. Total distance from parking is 0.2 miles, not as the crow flies but according to the route above.
When you find GZ, approach from the north so the charter sendings don't slay you as an intruder. Be aware that only those with an uncorrupted charter mark can visit the royal line. There is an outer shell of metal: leave the latter in place, remove the lid, and extract the inner container.
This is a letterbox hybrid. In addition to the normal logbook and trade items, it also contains a letterbox stamp, inkpad, and stamp book. Please do not remove the stamp, ink pad, or stamp book. THEY ARE NOT TRADE ITEMS!
There is a name on the inside of the container that will be of use in binding the destroyer.