Horrors, otherwise known as "When Cthulhu gets Bored" Options

[Mr. Mage]

So this may have already been gone over in a previous thread, but I couldn't find it. I am looking for more information on horrors. I realize that they are more of a story tool and don't really have too much in the way of game mechanics dedicated towards them, but anything like suggestions to source material to fiction about them would be helpful.

If you want to know why I want some info:
My next run has to do with the Runners being hired to acquire an artifact from a cult that is operating up in Massachusetts (wink wink) but unfortunately arrive at the tail end of some ritual. The artifact causes a mana spike capable of allowing at least part of a Horror through to our plane of existence. Think the end of Borderlands...or various stories by good ol' H.P.

Of course, from there it is entirely up to the players, though nothing that will drastically change the rest of the game-world (as in if the Runners can't stop it, Deus Ex Machina to the rescue).

I am looking for more source material on Horrors mostly so I can either get some inspiration or see if something else would fit into the SR lore better than this.

Thanks!