So I'm creating a scenario for my RL RPG group using the Night's Black Agents rules, which for those who haven't heard of it before, pits the player group of secret agents against a vampire conspiracy. My vampires, I've decided, are alien in nature - the original aliens briefly visited Earth a few decades ago and infected a number of humans with vampirism, and then ordered them to construct a habitat on Earth from which they can conquer the planet.
My issue comes from the fact that I don't really have much clues on how to build out the conspiracy so that it can get the materials they need, considering that non-carbon based life forms will operate almost completely differently on Earth! A quick perusal of le Google says that a leading hypothetical alternative to carbon is a silicon based lifeform, Crystalline Entity-style, which interests me because apparently Earth has relatively high amounts of silicon compared to carbon. But then the discussion breaks down into molecule variety and lack of solvents and other things that are over my head.
So what I'm looking for: If silicon-based life forms wanted to set up shop here on Earth, what kind of materials would they need to have their cat's paws appropriate? Is there a cooler, more out-there alternative than silicon-based life, and if so what would THEY need? This is just for a game, so pseudo-science and conjecture are totally fine here!