The Funcom title can be played for free with no limits by signing up to a Secret World account.
Users can earn an extra two days worth of free gameplay by completing 30 missions, as well as 1200 bonus points for the in-game store.
Defeating the Ur-Draug boss and completing the first dungeon, meanwhile, unlocks the Whispering Demon Ring, which grants a stat and XP bonus during the early stages of the game.
Set in modern-day locations such as London, New York and Egypt, players can join one of three secret societies to help battle mythical monsters.
The Secret World was released for PC in early July. Despite decent week one sales, it was unable to knock Diablo 3 off the top of the PC chart.
The Secret World's second DLC update was delayed following mass layoffs at Funcom.
> Read Digital Spy's review of 'The Secret World'
Watch a trailer for The Secret World below: