The Yellow Tower

The yellow tower is a structure built into part of the Silver Mountains directly to the east of the Granite Hold It is composed of numerous layers of sandstone brick which stretch from the base of the mountain to the top, connected by a single tower-like structure with a staircase to allow for travel between different elevations.
The purpose of the yellow tower was to be used as a signalling post to control and direct armies during the Grannr-Leskeln war. Fyrstbairn would climb to the edge of one of the platforms and conjure signals in the sky, most commonly protracted bursts of bright light, which could then be seen as small specks from other viewing platforms erected in distant regions. The signals could be interpreted based on colour, the duration of a single flash, and the amount and frequency of flashes, each of which corresponded to different meanings.
Most commonly, the tower was used to inform distant armies of the status of reinforcements, or to warn them of Leskeln movements in the area. The reverse was also possible: Armies would set up their own smaller messaging posts and flash signals back to the yellow tower. This was frequently used to indicate that the force had become engaged in a battle, or to relay movements back to command, among various other uses.
Owing to the extreme altitude at which the upper layers of the tower were situated, it was rare for human esoterikii to ever be deployed to play the part of signallers. In addition, the weaving of arcanums that produced a sufficiently large quantity of light to be visible at distances of hundreds of miles was remarkably taxing for humans, another contributing factor to why the tower was manned by the Fyrstbairn.
With the collapse of the Grannr, its successor states in the Landamar region never again projected force beyond their immediate borders; and so the tower eventually fell into disuse, many of its platforms crumbling away under the force of erosion.