On Track

Kiri's one-pager (PID=91812707) might be somehow misleading, she's not an example of any specific unit, so instead of a unit introduction, I just wrote about Envoys in general. I later realised it might be creating the impression of Envoys being an organisation similar to Nightingales or Yulin, so here's a clarification: "Envoys", as the description says, is just a term describing people chosen by the Engine, marked by their unique facial tattoos.

The outside frame of the tattoo was a manual addition created with a normal tattoo machine, used to mark where the real marking would appear. The actual, indicative part of a tattoo is the pattern inside the frame. Those will appear when an Envoy is actively carrying out the Engine's mandate or using their powers granted by the Engine. Envoys are Blue Heaven's representatives but they're also humans living their own lives, so it'll be helpful to distinguish their own deeds from those carried out on behalf of the higher power. The tattoo is, in a sense, like the siren light on a police car: a police car can still be used for daily activities but when the light is flashing, it means they're on a mission and they're exercising their authority. Of course, as a normal human there's nothing stopping you from getting a similar tattoo for yourself, but it'll be difficult to trick people with it because it's well-known that real Envoys can show/hide their markings at will, and that'll always be the first thing everyone would ask an Envoy-imposter to do.

In the drawing, Yesemo's pattern isn't showing, meaning she's not actively carrying out a mandate and she's not using her abilities (enhanced perceptions, marked by one vertical banner, Kiri's double-horizontal pennant indicates enhanced metabolism and motor functions). 

Envoys' enhanced abilities were granted so they could better carry out the Engine's mandate, but those abilities can be used at the Envoy's own discretion, making them valuable assets to human organisations also. As the only Envoy the Nightingales have, Yesemo usually takes the role of lead tracker in a team, but in this case, she asked Atsku'ama to take point, as an opportunity for the apprentice to gain experience. 

Not many units have more than one Envoy so a small team with two Envoys is a rare occurrence indeed, it's the infantry equivalent of a dual-carrier strike group. In the past this only happened during joint operations, or in rare missions where the opposition poses near-Envoy level threats but the situation prohibits sending more/larger teams. In this case, the Nightingales were there to assist Kiri on her own mission to track down Kuri.