The year's most hotly anticipated videogame lands Tuesday as the final installment of a "Mass Effect" trilogy immerses players in an epic battle for Earth.
The gripping science fiction adventure meshes powerful action and interactive storytelling that lets players shape which direction the saga takes, with decisions changing the outcomes of situations and the fates of in-game characters.
In a unique move, studio BioWare crafted the "Mass Effect" franchise in three parts with a compelling overall story arc and players' actions in one game following them into the next.
Allies made or friends lost in one game changes who is at the side of a player's character, and thusly their options, in sequels. Players can opt to not import characters' reputations from earlier games so they can start fresh.
Alliances promised to be paramount in "Mass Effect 3," which was billed as putting players "on the front lines of this all-out galactic war."
"The entire scale of the game is bigger than anything we've ever done," said "Mass Effect 3" executive producer Casey Hudson.
He touted the game as delivering "intense action, deep customization and raw emotional power."
The games pit the main character, a male or female version of Commander Shepard depending on player preference, against an ancient race of machines called "Reapers" intent on wiping out organic life in the cosmos.
The third version of the game opens with Reapers invading Earth, according to demo software released free online last month. Shepard was called on in the demo to enlist the help of races from other planets to fight the Reapers.
"You along with a team of battle-hardened soldiers are the only ones who can save Earth, and the galaxy, from complete annihilation," the game makers said in a release.
"Each decision and every action could have devastating and deadly consequences in your journey."
"Mass Effect" trilogy publisher Electronic Arts declined to disclose how many games had been pre-ordered, other than to say the number "well exceeded" those for the second installment.
Mass Effect software released on Valentine's Day quickly became the second-most downloaded videogame demo in EA history, behind only "Battlefield 3."
The franchise has received more than 250 awards and 100 perfect scores from videogame critics.
"Mass Effect 3" was priced at $60 and version were tailored for play on Xbox 360 and PlayStation 3 videogame consoles as well as personal computers powered by Windows software.
The Xbox version of the game was adapted to allow players to tap into voice and motion command capabilities of Kinect accessories.