Titan Quest: Atlantis is the third expansion for Titan Quest and OUT NOW for PC: http://n.thq.com/CEWn30oFVRB (requires the base game Titan Quest Anniversary Edition)
The Hero meets an explorer that is searching for the mythical kingdom of Atlantis, and together they set out on a journey across the western Mediterranean. The key lies in the legendary Diary of Herakles, rumored to be in the Phoenician City of Gadir, but their journey will take them beyond the edges of the known world…
Play a classic Titan Quest adventure in single player or with up to 6 players in co-op. Survive the Tartarus, an endless, wave-based challenge mode. Unlock new skills, spend all your excess in-game money on random loot and enjoy graphic and QOL improvements!
Source: YouTube video description