[Mark]

Like Mizu' said, character description a bit lacking. I would go so far as to say it's often vital to be able to describe your characters in a single beat, especially for a short story where you have no words to waste.

Become more aware of your 'voice' and what you are actually describing. Narrating the setting, characters, action, timeframe, emotion, all come together once you are aware, and the peice will live and breathe on its own.

-> Who are the Tsu? What do they look like? Why do they fight?
-> What do the Raven Guard look/sound/smell like?

These questions plagued me from the start and where difficult to imagine.

I liked the beat and flow of your action though. Being familiar with the Warhammer setting enabled me to see and hear the ping of deflected rounds and the crump of grenades as the Raven guard stomped the alien defenders. Very nice.

It's not even necesary to answer all the questions that might be in a readers mind about what's happening, but instead it suffices to offer only what is necesary for the readers to picture the events themselves.

Good job.