The main story of Tomb Raider is, Lara croft is trying to find her mother by following the clues her father left her before he died. This story line starts in Tomb Raider Anniversary, and continues Though Legend and Underworld. Anniversary explained what happened to Lara in her in her early days as she started her quest for her mother, legend continues the story and takes it to the next level and reveals more of her fathers secrets
Underworld takes traditional Tomb Raider-style gameplay to a whole new level, with better graphics, an expanded range of moves for Lara, more interaction with objects, and many more new features. The traditional "boss" battles, a feature of past Tomb Raider games, have been completely eliminated, and combat in general has been cut back in this game.
Visual, this instalment of Tomb Raider is cut above the others, being the first in the series to use motion caption, not only that but it also has visual feedback, the environment reacts to the player ( Plants move when touched, footprints are left behind) a new feature that makes the play feel they are making an impact on the world.
A bit of a warning here: The game is very buggy. Of course this isn't unusual most game have there problems but there are a few in Underworld that can prevent the player from completing the game,several of these cannot be fixed after the fact, except by replaying large sections of the game, but all are preventable.
There are 2 DLC's available to download, Lara's Shadow, a short chapter that tells the story from the Doppelgangers point of view, and Beneath The Ash's, another short level which adds on to the main story.
Over all the game is a defiant improvement on the franchise and is a must have for all Tomb Raider fans, it could do with more puzzles and exploring. But it still is a fun and challenging game to play.