Ubisoft pulled the plug on the Assassin's Creed: Unity season pass last month, offering a free game in its place as a replacement and apology. The freebie offer wasn't actually live at the time, but now is.
There are six games to choose from: The Crew, Far Cry 4, Watch Dogs, Assassin's Creed: Black Flag, Rayman Legends, and Just Dance 2015. Some restrictions apply, however: As noted by Rock, Paper, Shotgun (because I'm not eligible for the offer and thus can't look into it for myself), the free game must be on the same platform as Unity, which among other things means that for PC players, Just Dance 2015 is not an option. Dry your eyes.
They're also only being offered via Uplay—no Steam codes—and while the system is up and running, you may still experience some wonkiness: On my first attempt to log in I was unable to establish a secure connection, although a refresh got me through quickly enough.
The free game offer, which you may take advantage of at acu.ubi.com, will remain open until March 15, 2015. Ubisoft warned that seasons passes activated after November 25 may take up to ten days to register with its systems.