Scott Cawthon has created a Steam page for Ultimate Custom Night which is its own game rather than DLC for Freddy Fazbear's Pizzeria Simulator. In this game you will sit in an office and cope with as few or as many characters as you like from seven different FNAF games. Originally there were 50 characters, but then a new one jumped in...and you can see who she is in the trailer, so it wouldn't be a spoiler to name her, but why don't you go to the Steam page and check out the trailer yourself?
The game will be released on June 29 unless Scott pulls a Scott and releases it early, and it will be a freebie. And soon after the release I will sit back with a bucket of popcorn (buttered with the butter of all nations!) and giggle as I watch Dawko suffer as he tries to survive 50/20 mode.