1. Introduction of the game
Titan Quest is an action role-playing game set within a mythological backdrop where players embark on an epic journey through ancient civilizations such as Greece, Egypt, and Asia. Developed by Iron Lore Entertainment, the game draws upon the rich lore and legends of these cultures, pitting heroes against legendary monsters and formidable gods.

2. All characters and levels of the game
Players in Titan Quest create a character, selecting from various character classes. They can combine Masteries, which include Warfare, Defense, Earth, Nature, Rogue, and Spirit, among others, to create unique builds. The game features expansive levels across its various acts, with settings ranging from the lush fields of Greece to the deserts of Egypt and the mysterious Orient. Further expansion packs like "Immortal Throne" and "Ragnarok" introduced additional Masteries and landscapes, such as Hades' underworld and the Norse realms.

3. What attracts users most to the game
Titan Quest captivates players with its rich, classical mythology and the depth of its character customization. The ability to mix different Masteries to create distinctive playstyles and the allure of discovering rare loot keeps players engaged. Additionally, the visually stunning environments, filled with detail and color, along with the robust mythological storyline, contribute to the game's allure.

4. Why it is popular
Popular among fans of the ARPG genre, Titan Quest offers a blend of thrilling combat and strategic gameplay. Its popularity is bolstered by its extensive modding community, the nostalgia of traditional isometric ARPGs, and its timeless storyline. The game strikes a balance between accessibility for newcomers and in-depth mechanics for seasoned players, ensuring a wide appeal.

5. When the game was released and how many versions are currently available
Titan Quest was originally released on June 26, 2006. Since then it has seen a number of versions and expansions, with the "Anniversary Edition" released in 2016 to celebrate the game's 10-year milestone. This edition combined the original game and the "Immortal Throne" expansion, along with numerous updates and enhancements. Subsequent expansions like "Ragnarok" (2017) and "Atlantis" (2019) further extended the game's content.

6. The most difficult part of the game
For many players, the most challenging part of Titan Quest lies in its endgame content, including high-difficulty areas like the Labyrinth of the Minotaur and the Atlantis expansion's Tartarus Arena. Here, players face the toughest enemies and must use all their skills and strategic acumen to survive.

7. Strengths and weaknesses of the game
Titan Quest's strengths lie in its compelling mythology-inspired world, rich character customization, and satisfying loot system. However, weaknesses include occasional balancing issues, and some players might find the combat less dynamic compared to modern ARPGs. Additionally, while the graphics were updated in the Anniversary Edition, some aspects still show the game’s age.

8. What other games have been developed by the same developer
Iron Lore Entertainment, the developer of Titan Quest, also worked on an expansion for Dawn of War, titled "Soulstorm," before closing its doors in 2008. The intellectual property was later acquired by THQ Nordic, which has since been involved in developing newer content for Titan Quest and overseeing its expansions.