The Crimson Dawn originate from somewhere in Cathay from what can be gathered. They appear from glowing portals, from somewhere called the Shadow Veil and disappear back to the same place. These portals can appear almost anywhere, but seem to do so close to transport circles, but rarely within them.
From these portals they send in humanoid looking creatures in waves of 10 or a dozen. These creatures look human, but at closer observation they are less than real. Disappearing in a shadowy burst upon their deaths they throw their lives away without a second thought. They also detect as if unliving, shadow creatures in origin and unlike any unliving seen in the Heartlands.
Each group is lead by a human, however. This person seems able to open the portals to the Shadow Veil without access to ritual magic and travel back and forth bringing waves of Undercloaks with them each time. The leaders give little information as to why they are doing what they are, usually just ordering the Undercloaks to attack and assisting in the fighting.
What the plans are of the Crimson Dawn is unclear, and what they want done with the Tengu is still a mystery. Comments about "tests" and similar have been cryptic in the extreme. Kidnap attempts have been made, rather than assassinations, on several members of the Tengu. But what the long term goals of the Crimson Dawn have yet to be revealed.