Dishonored

"Choice and consequence" may be the action-adventure cliché du jour, but being able to define your own combat style through a suite of overlapping toys is definitely up there too. Pretty much ever since BioShock invited us to paralyse splicers with electricity and then whack 'em with a wrench, everyone's been at it.

Typically though, with great power comes great limitation, and in order to keep worlds like Rapture from descending into anarchy mechanically as well as narratively, designers have become jailors, building environments around you like gilded cages that lock you away from too much imagination.

So it's pretty interesting to sit down and watch Arkane Studios' Harvey Smith and Raf Colantonio play around with the tools you get in Dishonored, their first-person stealth game about an assassin with magical powers, because they insist they've taken the opposite approach.

Whenever they introduce a new power or tool during development, within hours someone on the team invents an exploit that kind of breaks the game, like coupling the high-jumping ability with a partial-teleport to travel vast distances and meddle around in the rafters of the world. Rather than shut that option down again, they then think about how they can design levels that benefit from it.

Dishonored is set in a retro-future industrial world where human civilisation is crowded onto four islands in a large and turbulent ocean, and this adventure takes place in the whaling city of Dunwall, ruled over by an oppressive regime against whom your character, a voiceless blank slate called Corvo, has a grudge to bear.

Corvo's been wrongly accused of murdering his employer, the Empress, and the game is about his quest to visit revenge on the people who framed him. In the demo we're seeing at QuakeCon, Corvo is on the tail of a dodgy lawyer who is rinsing the local population for their homes and possessions, but it's up to you how you prosecute your agenda.

Armed with various powers in your left hand and a short, cutlass-like blade in your right, you can hack and slash your way through melee combat, but you can also do things like bending time – pausing enemies and queuing up bullets a couple of inches from their faces, then unpausing – or blasting them out of windows on bursts of concentrated air.

You can also possess people and animals – like rats – and use them to travel around, scurrying through ducts into servants' quarters and then resuming Corvo's original shape once you're inside. Again, it's pregnant with game-breaking potential, but Arkane doesn't seem to mind.

Smith and Colantonio answer most questions with examples of combinations people have come up with. For example, strapping a mine to a rat, possessing the rat and walking it into a crowd of enemies, then possessing something else and getting out of there before the mine explodes.

Another one they rather like is pausing time just after an enemy has fired his gun, possessing him and walking him in front of his own bullet, then getting out of there and letting him suicide himself.

Dunwall is an interesting place to do all these things. Arkane's art director is Viktor Antonov, the guy who imagined Half-Life 2's City 17, and his touch is evident right from the first frame of our demo, staring at the reflection of a bleak, overcast sky in a glassy ocean that stretches as far as the horizon.

There's a whaling ship coming in – its blubbery mass suspended above the deck by a huge H-frame crane. There's no electricity in Dunwall – although this is not Earth, the architecture and period dress is decidedly Victorian – but the volatile whale oil has recently been harnessed into various echoes of Nikola Tesla, like Wall of Light barricades that zap anything that passes through them into mists of blood.