Rebellion’s Aliens vs. Predator and Gearbox Software’s Aliens: Colonial Marines have been pulled from Steam on January 1st, 2015. Both titles are no longer purchasable from Valve’s digital platform but they still can be activated and accessed via your Steam Library.
While no official explanation has been given as to why both games aren’t available through Steam any more, this could potentially indicate the end of SEGA’s license to digitally distribute these two titles.
Other licensed games, including several of Activision’s Marvel titles as well as Family Guy: Back to the Multiverse and Ice Age 4 were delisted from Steam in time for the new year.