The Diamond Spider was rare species of spider that lived in space. It produced diamonds in its body and could make them into webs. It fed on the metals from asteroids and spaceships it caught in its web.
The Doctor, Amy and Rory arrived on a spaceship which had been caught in a diamond web. Deciding it was valuable and would earn them a lot of profit, the Empire Of Eternal Victory attacked it in order to capture it and use it to create diamonds for themselves so that they could be rich. Instead, the Doctor stopped their plan and the spider was allowed to be free. (PROSE: Web in Space!)