With most great games, you see ’em coming. Not that many teams have the creative and technical chops to create superlative interactive entertainment, the kind that gleefully whisks you to a faraway place you want to spend dozens of hours exploring. And so the leaders in various niches are usually well known.

But every once in a while a game arrives out of the blue that redefines expectations for an entire genre. A game like The Witcher 2: Assassins of Kings. If you enjoy single-player role-playing games on PC, you simply must play The Witcher 2. Innovative, unflinchingly mature and richly imagined, it is driven by fascinating, finely nuanced characters navigating a fantasy world of dark political intrigue and ambiguous morals.

The world of The Witcher is gothic, soulful and intelligent, yet mercilessly brutal. Innocent people die, and still almost all the characters consider themselves perfectly justified in their actions. After all, one man’s terrorist is another’s freedom fighter, and which you consider noble depends on your personal circumstances. As the Witcher, an independent, mystical warrior set amid warring medieval kingdoms, you will have to decide what justice means to you.

In the real world, many nations know about being riven by powerful external forces, about genocide, the death of innocents and the choices people must make in the face of soul-shaking horror — not least Poland. So as you become enveloped in the world of The Witcher 2, it gradually comes to make sense that it is based on the work of the Polish novelist Andrzej Sapkowski and was created by the Warsaw developer and publisher CD Projekt RED. In Poland it is considered a leader in digital entertainment; the Polish prime minister, Donald Tusk, gave President Obama a copy of The Witcher 2 during Mr. Obama’s visit there in May. (The game is being published in North America by Atari.)