- Raps have enemies they're running from.
- They find an alien, not a Rap, in a downed spacecraft. Very much biological rather than mechanical.
- It's reported that the Raps' enemies destroyed the Factory they had on the Moon.
- They go to a resistance camp that has captured one of the Raps. It's seen that the ball of light in their heads is like their soul/consciousness/etc. It understands what they say. It reveals that they came to Earth because they were escaping their enemy (see above). They're using humans as a labor resource, while also building defenses to be used against said enemy. Last thing it says is: "Our enemy is your enemy, we are your defense."
- Snyder reveals that the Raps agreed to protect humans as long as they were provided slave labor (to build the defenses mentioned above).
There hasn't been much about them since then, but a new character was given tech by them (food that can be grown in labs), and there's also a polymer that can stop bullets that's presumably from them as well.
Oh, and the Raps have identified so-called Outliers (mostly ex-military, of which Will is one) who they keep in pods secluded, so they cannot cause trouble, but apparently they're also planning to use them as a defense against their enemy.