Several months of personal observation paid off when a Shadowlands incursion struck at the Kaiu Wall. Utilizing a powerful lantern and a concave mirror, one of the towers near the wall started flashing the light in various patterns toward one of the more distant towers. They responded after a short time, and rather distant Crab forces began to arrive only twelve hours later -- the time it would have taken to dispatch a messenger to the unit's station.
This systems only seems to be used for signaling about attacks against the Wall from the Shadowlands. I asked one of the Crab samurai about it, and although reticent at first, later admitted there was a code in use, and that only Shadowlands-related news was relayed over the towers -- if the codes were broken, it would be too simple for someone outside the system to inject false signals to make for good general use.
To my understanding, the system is the brainchild of one Hida Sukune, a son of Crab Daimyo Hida Kisada and a master strategist, and orchestrated by the Kaiu Battle Masters. Indeed, I find it likely that only this combination could have put such a system into practice. The rumor that the mirrors can also be used to focus sunlight into a burning intensity is only one consequence of this.
----------
Used as burning mirrors, the signaling mirrors can act as a basic "Summon Fire" spell on a flammable target. They can only be used in this manner during the day.
Return to the Intelligence Bureau.