The SPI organization is overseeing the centennial signing of treaties, and Rake is host. So pretty much all the non-humans are at the party, and someone with a grudge against SPI and Rake has a new gadget they want to try out.
They create a pocket dimension and trap everyone in it while teleporting all sorts of things in. Amazingly enough, the only ones who actually die are a portal mage, and the one who killed him. Then again, most of these various peoples are used to fighting, so they treat it like a game.
In the end, Rake gets a promotion he wasn't exactly wanting, the bad guy is still out there, and the gadget, being only a prototype, neutralized but how long before another one is built. I just kinda hope that doesn't become a go-to theme in this series.