Betrayals are great plot motivators in video games. Or developers seem to think so, because at least one member of any given game's cast inevitably just hangs around on your side long enough to crap in your salad. A lot of betrayals don't make much sense. Or they come out of nowhere. Or worse still, they're so predictable that they the only one surprised is the moron protagonist. But every once in a while, a game comes along and pens an act of duplicity so daring that it manages to shake the foundations of everything you thought you knew. Here are seven such moments. Oh, and at least one of these games is from the past year, so:

7. StarCraft – Arcturus Mengsk

It's hard to peg Starcraft as sweeping epic of the human condition, what with the countless marines you so casually throw into the meat grinder just to delay an opponent's expansion. But the campaign of the first Starcraft painted a pretty bleak picture of advanced space-politics. The Confederacy has an iron-grip on human activity across dozens of planets. Even as two alien races emerge to challenge human dominance, colonial oppression runs deep. You turn to Arcturus Mengsk, a cunning strategist and master of oratory to liberate your species in the sector. Mengsk, his Lieutenant Sarah Kerrigan and the nameless commander controlled by the player are able to strike a few key victories against the Confederacy.

But ol' Arcturus has a few more plans than just easing living conditions under Confederate rule. Manipulating the two new aliens, Mengsk wipes out an entire planet, leaving his second-in-command for dead in the process. After Mengsk's betrayal, no human force in the galaxy has the strength to challenge him. And after supplanting the Confederacy, his government proves to be just as intrusive and just as brutal.

6. BioShock – Atlas

Rapture is an unnatural monstrosity; it's a cold and hollow place where everything that breathes (and many things that don't) stalk you at every corner. Fortunately you've got Atlas, your radio guide and the only friendly voice 20,000 leagues under the sea. He does all the things you could want a trusty off-screen sidekick to do: he gives you a heads up on incoming threats, points you toward your objectives, and supplies you with everything you need to survive Rapture. And when his family is unceremoniously murdered, you realize just how woefully backward Rapture is to allow such tragedy to befall such a kindly soul.

Until, of course, you discover that he's leading you around like his little lap bitch, having you kill off all his enemies with a tug of a heartstring or a polite hypno-request. Atlas's betrayal is effective not because it was unexpected—even though it was—it was effective because he was the only person that was unequivocally on your side, and once he's gone, you find yourself all alone in a mad, savage world.

5. Grand Theft Auto: Vice City – Lance Vance

As mentioned, betrayal is usually a fairly predictable staple in video games. If things are going well, it's probably because one of your asshole NPC buddies is setting you up. Betrayals usually come with a few warning signs, signs that are especially present in the Grand Theft Auto games where you play a criminal committing crimes… usually against other criminals. But what makes Lance's betrayal effective isn't the surprise of it, it's the logical inevitability of it.

Tommy Vercetti is a psychotic, egotistic, amoral thug (which makes him just another Joe Schlub in the Grand Theft Auto universe). Lance was a friend and ally when Tommy needed one, he was impulsive but reliable. Tommy berates Lance for his failures, ignores his successes and treats him like a lackey by the end of the game. Of course Lance betrays Tommy and of course Tommy deserves it. But if Tommy showed a little more loyalty to those in his own camp, the whole thing could have been avoidable, calling into question who really turned on who.

4. Prince of Persia: The Sands of Time – Princess Farah

Farah and the Prince are a match made in heaven. They're both snide, spoiled and insecure. They're also the only survivors in a kingdom turned zombie-sand-demon playground. Farah and the Prince were more than just a typical video game romance subplot. Their interactions were central to their character arcs, the two played off one another, bickering and debating and growing closer and more personally involved with one another. When the vizier finally traps the pair in the palace baths, all hope seems lost. Their mission failed, they settle for one last night of passion before chaos swallows the earth.

Except actually Farah has to get up to work really early so she's really gotta get going. Also, she's taking the dagger of time with her—y'know, that thing that's been keeping you alive this whole time—so she can harness its power for herself. Farah's betrayal isn't very sudden, or even really all that unexpected, but what makes it effective is just how much the two leads mean to one another by the time it happens.