Master art thief Charles Deckard creeps cautiously towards the box. Pandora's Box, to be exact. It sits on top of a raised platform in a darkened New York museum room. Hired by the mysterious Professor Lefey, Deckard knows not of the havoc, destruction and chaos he is about to unleash upon the world. All he cares about is swiping the box's valuable innards and getting the hell out of there undetected.

Deckard, a suited and booted man who's the antithesis of your typical muscle bound FPS marine, puts his hand on the box. Bad move.

The box closes in around Deckard's hand, clamping him to its outer casing. Cue the spewing forth of explosions, beams of red fire and all manner of madness as the museum is shook to the core. All those legendary beasts of myth and lore, the ones your parents spoke about in bed time stories - well they're real. Very real. And now they've been let loose. New York, indeed the world, will never be the same again.

The cutscene ends and Legendary turns Deckard over to the player, ie, you. Deckard, hopefully feeling slightly apologetic, has been branded by the Box, resulting in a mark on his left palm. He's now responsible for building a new box and sealing the game's army of beasts away for the last time. Bother.

Right now though, there are more pressing concerns. Controlling Deckard you make your way out of the crumbling museum, past falling structures, exploding walls and scores of petrified art-lovers. In this first stage there's little more you can do but walk, crouch and jump your way past the chaos, eventually finding the exit. It's here, with the streets of New York spiralling out in front of us, that we can see the full, shocking results of Deckard's handiwork. And it 'aint pretty.

A gryphon lands on the roof of a NYPD car, sinks its deadly claws into the sheet metal, lets off a deafening roar and flies off, vehicle in tow. You follow its path and see a hundred more gryphons circling in the skies, ready to pounce on the fleeing civilians below. The red beam emanating from Pandora's Box emits an all-encompassing pulse, knocking people off their feet and thrusting cars into the air. Disoriented, you run for cover, struggling to avoid the devastation. We nearly soil ourselves when we turn a corner to find a man savagely eaten alive by a gryphon, which then flies off with the lifeless body in its mouth. And then we see the crowning touch. In the distance cars, metal and trucks come together to form something. Eventually you realise exactly what's facing you - a six story tall titan made from the fabric of New York City itself. It smashes an arm down into the street, flinging twisted metal in every direction. It looks like Independence Day spliced with Jurassic Park, except with you right in the thick of it.

It's already looking far superior to Spark's previous next-gen effort

Phew. Talk about opening sequences blowing your socks off. We haven't seen a game opening this impressive since BioShock's entry into the underwater city of Rapture. And like that sequence Legendary's opening serves in part as a technical showcase, intended to grip you by the shoulders and shake you like a rag doll, and in part as a cleverly disguised tutorial. After Deckard is branded we quickly learn that he now has the ability to siphon health-giving "Animus" power from defeated creatures. Legendary works like this - you get health from the creatures and weapon ammo from humans.

Speaking of the humans, Legendary's story is one of two shadowy organisations which battle against each other for Pandora's Box itself. The Council of 98, a UN style organisation with hidden bases under the Houses of Parliament in London and Times Square, were the original creators of Pandora's Box, and have been trying to prevent exactly this kind of catastrophic event for years. In direct opposition to the Council is the Black Order, which believes in progress at any price. It likes genetic testing, gene splicing, cloning and nano technology. The aforementioned Professor Lefey, who hired Deckard to nick Pandora's Box, is part of the Black Order. It wants to try and harness the Box's power for its own personal gains. Evil.

There's no denying that Legendary is action packed

While you'll be facing off against members of both organisations in locations as exotic as New York, London (Big Ben gets destroyed) and Durham (yes, we said Durham, the Black Order is holed up there), Legendary's creatures are the stars of the show, even stealing the scene from Deckard himself. The game will end up with between 10 to 15 different creatures, most of which will be variants of the base creature classes, including the Werewolf and the Gryphon. The Werewolf, with its huge, deadly claws, can climb on walls, ceilings and generally defy gravity. Unlike the grounded human troops you fight in the game, werewolves will dart about surfaces, making them much harder to kill, and pick up in-game objects to chuck at you. They'll regenerate too - you can see their skin healing after you tear it off with weapons fire. The Fire drake is a creature of living lava. Not only can you be burned by its body but it can set the game world alight. That fire can then travel, burning up more of the environment dynamically, keeping things nice and fresh each time you encounter one. And we're told the Shadow of the Colossus-esque Titan class creatures, like the Golem we described at the beginning of the preview, won't be able to be killed with conventional FPS weapons. Developer Spark Unlimited isn't giving away much, but has told us that you'll have to use the environment to destroy them. Interesting.

Taking on the game's beasts on their own sounds cool enough, but taking them on in a gritty three-way street battle, involving werewolves, members of the Black Order and you, sounds even cooler. Lucky enough, we got our grubby mitts on an Xbox 360 pad to do just that. Legendary plays very much as you'd expect a gritty FPS would, with traditional dual thumbstick controls, a sprint button, assault rifles and shotguns, so it will be extremely easy for FPS fans to get to grips with the game. The level we played started with a narrow residential street shoot out. The Black Order are battling werewolves on the streets, in alleys and in buildings themselves. We have a decision to make - kill the werewolves, then deal with the Order, kill the Order then deal with the werewolves, let them kill each other or storm in and run and gun. We locked and loaded and stormed the streets.

Werewolves need to be decapitated to be killed (we found a close range shotgun blast did the trick). Otherwise they'll gradually regenerate. If you build up enough Animus you can do a force push style move, useful for crowd control. A Werewolf is being kept in a cage - what to do? Release it and hope it helps with the Order, or leave it there, its claws far from your neck? We approach a clearing off the beaten track - an imposing Minotaur is making short work of some Black Order troops. It turns on us, smashing through walls as if they were paper thin. It tears a Celtic cross out of the ground, converting it into a devastating club. We die.

The enemies you face can be pretty enormous

It's clear that Legendary's combat can get pretty crazy pretty quickly. It feels like an FPS arena game at times, which is no bad thing. We don't know much about the multiplayer offering right now, but what has been confirmed is Legendary will support four versus four games with each team playing as either the Black Order or the Council of 98. To spice things up a bit, AI controlled creatures will be running around the multiplayer maps, ensuring the three-way fighting from the single-player campaign makes a strong appearance in the multiplayer. Expect the traditional deathmatch and team assault modes too, but there will be one or two surprises thrown in - including Safari, where both sides hunt the game's creatures against a time limit.

Even at this early stage, Legendary instantly looks a lot better than developer Spark Unlimited's last FPS, the disappointing Turning Point. Built on the Unreal Engine 3, hardened FPS fans might be thinking: "here comes another generic FPS", but the concept feels fresh - the man versus myth idea is one that's piqued our interest. Legendary is certainly worth keeping tabs on. Look out for a closer look soon.

Legendary is set for release on Xbox 360, PS3 and PC in late summer. A demo is planned for sometime in June or July.