The 10-year anniversary of Titan Quest, the Diablo-esque action RPG, is being celebrated today with the surprise release of Titan Quest: Anniversary Edition. It's available at a steep discount for its first week, but you may already own it without having done anything.

THQ Nordic announced the updated version of the game today and revealed that anyone who owns Titan Quest, Titan Quest: Immortal Throne, or Titan Quest Gold on Steam has received the new version for free. According to a press release, that puts it in the hands of more than 1 million people already.

You don't need to do anything to get your freebie--if you own one of the qualifying games, Anniversary Edition should now be in your Steam library. For those who don't own any of them, you can pick it up on Steam or GOG right now for $5, a 75 percent discount on the standard $20 price it will be available for beginning on September 7.

Anniversary Edition consists of the base Titan Quest game and Immortal Throne, both of which are described as having been "completely reworked in terms of multiplayer, stability, performance, balancing, AI, and much more." New resolutions are supported along with other visual options, but it's important to note this is not a remastered version with dramatically improved graphics.

A grand total of 1,261 changes have been made. Obviously not all of these are hugely significant, but you can see the full list of them here. For a broad overview, here's what THQ Nordic says is new:

Restored and improved multiplayer functionality, including new features like a built-in voice chat and NAT resolving for best multiplayer connectivity

Support for more resolutions, larger camera distance, and scaleable UI size

Improved performance and general stability

Support for modders through new modding options and a fully integrated Steam Workshop

Complete balance rework with improvements to all Masteries, damage types, unique items, and sets

Countless bug fixes and other improvements, including ten years' worth of community fixes

Increased challenges and rewards for larger parties and on higher difficulty levels

Dozens of new heroes and bosses to encounter

Improved enemy and pet AI

Quality of life features like higher stack limits, quick item pickup, a larger stash, and a speed setting

Reduced cheating with curbed exploits, removal of test items, and mod comparison in multiplayer

Steam Friend Invites

Steam Achievements

Steam Trading Cards

The decision to offer Anniversary Edition ties into THQ Nordic's recent decision to revive the THQ brand.

"After our name change from Nordic Games to THQ Nordic, we wanted a running start for our new identity and had to think about how to begin the new era with the most positive connotation possible (for a publisher)." This led to a discussion where it decided it needed to be grateful to fans, landing on free stuff as a good way to show that.

Titan Quest was originally released for PC back in 2006, with the Immortal Throne expansion arriving a year later. It was developed by Iron Lore Entertainment, which shut down in 2008.