Oddly, Jason Voorhees' appearance in Mortal Kombat X doesn't coincide with one of the regular Friday the 13ths we see throughout the year. You've missed an opportunity there, Warner Bros.
Instead, the masked slasher appears in MKX from tomorrow (May 5) for those who own the Kombat Pack add-on, while those who don't have to wait until May 12 to purchase the big hunk of horror separately. Do you want a trailer? It's not for the squeamish:
Those owning the Kombat Pack also get three horror-themed skins: Vampiress Mileena, Kraken Reptile and Pharaoh Ermac. If you don't own the Pack it's $8 (£6.49) to purchase Jason and the horror skins together, or $5 (£3.99) for Jason on his own/$4 (£3.29) for just the horror skins.