Update your game, right-click the game in your steam library overview or hit the play button in your steam client after you ran the update.
What will that get you?
The option to start and play the Halloween Edition, in addition to the "normal" game!
And, as we are always trying to grab you and tear you even deeper into our trashy nightmares, here we go with 20 steam keys for
http://store.steampowered.com/app/266050/
VQQBR-2LQLT-KCTKH
HR3TT-8RFN5-L47PV
EDBQQ-NF2R5-KRNJM
K5639-BR58Y-493ZL
JIL83-LJVB0-0L362
YLA9V-F47W7-3TDR2
MFGT2-ELBA9-0RLLJ
5VXX2-WKW5H-Z9IKM
HGIX6-LENZC-DTF05
CA9W0-QBX49-6TZ7J
4I04X-P2Z3F-FGYXY
A5RK0-A73EY-52XQ2
HNWEK-APK2H-4CJ99
VHFX7-0R664-98A5L
ZA7R5-9QMYM-JR7HR
FKVPP-TX2X2-LNEXP
NN9DZ-4YFHT-JTM97
JEKNQ-3G5KX-EIQ4C
I7WVR-I36FX-M49D9
MG9L7-YWQ0C-PN9C0
(First come, first serve, please comment which one you grabbed!)
Once again, Happy Halloween!