http://steamcommunity.com/games/475150/announcements/detail/597112859861313840
Vienna (Austria), August 31st: THQ Nordic releases a surprise title on Steam called Titan Quest Anniversary Edition for the game’s 10-year-anniversary and gifts the game to everyone calling either Titan Quest, Titan Quest: Immortal Throne or Titan Quest Gold their own on Steam. So, in numbers, more than 1 million people will automatically find the game in their library starting today.
Titan Quest Anniversary Edition contains both Titan Quest and Titan Quest: Immortal Throne which have been completely reworked in terms of multiplayer, stability, performance, balancing, AI and much more. In rough numbers, this translates to roughly 1.261 changes to the original version 10 years ago.
For the detailed changelog, refer to this link: http://titanquestgame.com/pcchangelog/TQ_AnniversaryEdition_FullChangelog.txt