Awww. Jut saw on his patreon that apparently this was the final part of this chapters story, and the next one will start a whole new story focusing on a new chapter. So we'll probably never figure out WTF just happened.
I literally don't know anything about WH40k except that it is a board game with cool miniatures and the universe I'd some sort of cryptofascist nightmare blend of Dune, exaggerated hyper masculinity, dark ancient majik and power levels that make MCU look consistent.
I've always admired it for its sort of quiet purity and external opacity. It's not for you unless you're already into it and it's internally self-consistent but keeps growing.
So here's what your mom or ignorant little brother thought was happening :
Those space armor dudes are tasked with guarding an ancient evil ball. If nobody volunteers as a sentinel to watch over it, it'll reach out into this world and things will go mad south.
They've been watching it for decades or Millenia and sometimes it's inert and sometimes active. Reports of odd behavior make the space guys come to check in and make sure it doesn't evil all over the place.
The volunteer is a survivor from the early "research" and one of the space guys who figured out how to restrain it somehow or at least warn space guy hq. he's been meditating abd watching for an unreasonably long time
Eventually evil ball activates either a plan or a normal life cycle behavior, infects the sentinel /watchman, and the observation squad executes him to cut off the ball's external influence.
The ball retaliates or feeds by sucking n space guys and one of them avoids being digested by firing at the last second to blow off his captured hand - but is sucked into the evil Crom palace dimension or palace of evil ancient ones - possibly long dead and the ball is just their of evil magic tech exhibiting a node in our space guy universe /dimension.
Now he's gonna check it out for treasure or tech for the King or emperor or find a way out.
I eagerly await my correction on probably every single notion the typed.
But it's still badass.