"Tomb Raider: Underworld" is now free to play via Square Enix's cloud gaming service, as part of the build-up to 2013's addition to the series in March.

Lara explores Thailand, Mexico, and the Arctic in 'Tomb Raider: Underworld.'

Added to the Core Online service in late December, "Tomb Raider: Underworld" is generally considered to be one of the better "Tomb Raider" games and marked something of a return to form for its adventurous archaeologist Lara Croft.

As far as the Core Online streaming service goes, its games (which include "Hitman: Blood Money" and "Mini Ninjas") are presented as free-to-play on the basis that players will watch ads every 20 minutes or so; those interruptions can be avoided by stumping up cash to purchase the game or unlock later levels ahead of time.