It's hard to conceive what PC gaming would currently be like had Blizzard not released World of Warcraft. Four years, two expansion packs and tens of thousands of man years of consumed free time later, World of Warcraft continues to steamroller over its competition in the sales charts, with a cackling goblin at the controls, no doubt laughing all the way to the bank in Booty Bay. Wrath of the Lich King was already a phenomenal sales success within 24 hours of its release, selling a mind-boggling 2.8 million copies. To put that into some kind of context, that's almost double the total sales of Warhammer Online to date, which had been widely predicted to put a significant dent into Warcraft's subscriber figures. World of Warcraft has re-written the rule book on how to make mass-market video games, and with Wrath of the Lich King Blizzard is tearing up its own rule book and replacing it with something far bigger and grander than before.

One of the first things that strikes you when you play Wrath of the Lich King is the sense of scale. The new continent, Northrend is absolutely immense, both in terms of sheer area and the grandeur and diversity of the design. There are ten new map areas and the largest, Dragonblight, surpasses anything seen in Azeroth or Outland by a significant margin. Rival dragon clans (called aspects) battle in the skies, burrower worms and giant elementals fight for the control of frozen caverns and the undead Scourge lay siege to Horde and Alliance outposts alike. Hovering ominously over it all is Naxxramas, a high-end dungeon dripping poisonous ichors over the plague fields outside Wintergarde Keep.

And that's just barely scratching the surface of Dragonblight alone. The other map areas show a similar level of diversity, making Northrend a far more interesting and varied place to be in than anything to be found in Azeroth or Outland. Maps typically have around half a dozen quest hubs each, meaning that levelling is still comparatively swift, despite experience point gains in excess of one and a half million points per level being required. By the time you have accumulated a couple of levels beyond seventy, you can expect to realistically quest in Borean Tundra, Howling Fjord, Dragonblight and Grizzly Hills, giving you access to nearly half of the content in Northrend relatively quickly.

Texture quality and draw distances are much improved for Wrath of the Lich King.

If you were expecting Northrend to be simply wall-to-wall snow and ice then you're in for a pleasant surprise, as not only does Northrend have a wide variety of landscapes but is also substantially prettier than anything to be found in the World of Warcraft thus far. Each zone has its own distinct character, but unlike some zones in Azeroth and Outland, which are largely homogeneous in aesthetic, in Northrend you can find a tremendous amount of variation in a single zone, including snow-capped mountains, frigid coasts, volcanic springs and zombie-infested farmland. Early highlights are the geyser fields beyond Fizzcrank Airstrip in Borean Tundra, the spectacular frosted island mountain of Coldarra, the tall cliffs and waterfalls of the Howling Fjord overlooked by the imposing Utgarde Keep and the pine forests of Grizzly Hills. Later you will be treated to the lush, humid jungle of Sholazar Basin, the frozen wastes of the Storm Peaks, the intricate ziggurats in the Ice Troll city of Zul'Drak and the sombre ruins and ethereal glades of Crystalsong Forest, where the sanctuary city of Dalaran floats in the sky, a safe refuge for the battle-weary. Finally, there's Lake Wintergrasp and Icecrown, the home of the Lich King himself.

Of all these new zones, Lake Wintergrasp is the most unusual, given that it is entirely devoted to objective-based PvP combat and siege warfare, even on PvE and role-playing servers. This zone showcases the expansion's most eye-catching innovation, the new mounted combat system, which gives you direct control over all manner of siege machinery, from defensive cannons to tanks, goblin shredders and aerial mounts. Unfortunately, the area is not immediately accessible, as it is isolated by impassable mountains and may only be reached once you have purchased the cold weather flying skill at level 77.

Not all of Blizzard's efforts since the release of The Burning Crusade have been devoted to creating the new continent of Northrend, however. Graphically, the game is noticeably improved, though perhaps not in the way you might expect. Rather than retooling the 3D engine to provide greater detail for each of the models, Blizzard has instead decided to improve texture quality and draw distances, as well as implement new special effects and real-time shadows. The result isn't a dramatic difference in visual quality but rather a broadening of the canvas, reinforcing the sheer scale and ambition of the expansion pack's design, without sacrificing any of game's playability at lower PC specifications. World of Warcraft has drawn some criticism in recent years for its stylised, cartoon-feel visuals, but any lack of detail in the models is more than compensated for by the terrific texture art.

Death Knights are terrific in both play style and aesthetics. Just look at that armour!

There's also very little reuse of buildings and structures from the previous continents in the game, making Northrend feel distinct from Azeroth and Outland, but still a part of the overall game world, thanks to a consistent use of architectural themes for the two playable factions. A greater emphasis has also been made on bringing the story to the fore, allowing players who are interested in the plot to get immersed into the lore more easily. Part of this refocus to a more story-driven experience is due to Blizzard's aim to reignite interest in the Alliance versus Horde conflict, which was sidelined by the battle against the Burning Legion in Outland. While the two sides do still have a common enemy in Arthas' Scourge, hostilities between the Alliance and Horde are very much in progress again. Beyond the PvP Mecca of Lake Wintergrasp, other PvP objectives are able to be fought over throughout Northrend, adding an extra incentive to hone your 'ganking' skills.

Blizzard has made other tweaks and improvements as well, including a new profession (Inscription, which uses glyphs to modify class spells) and more cosmetic changes, such as new haircuts. The largest change to the game balance, however, has been the introduction of the Death Knight 'Hero' class, which has already proved to be immensely popular. Even if you have no intention of playing a Death Knight character all the way up to the new level cap of 80, it is worth rolling a Death Knight just to get a taster of the class and finish their starting area: The Scarlet Enclave, beyond the Eastern Plaguelands.

You start your journey as a Death Knight in a Scourge necropolis, called the Ebon Hold, taking orders directly from the Lich King Arthas himself. The Ebon Hold quest chain is well implemented and gives players early access to some of the features available later in Northrend; including mounted combat and instanced quest events that change the look and feel of the map area, depending upon the section of the quest chain you're completing. Particular highlights are the battle for Tyr's Hand that requires to you to soar into the fight on the back of an undead ice drake, and a climatic assault against the Argent Dawn at Light's Hope Chapel. The class itself is a joy to play and may quickly become a favourite with many players. It is an intriguing hybrid of a tanking class with a high damage-per-second rating, and should you pursue the Unholy talent specification, you will have a non-time-limited pet ghoul to provide extra muscle and may additionally summon a gargoyle in for an airstrike once every few minutes.

This undead dragon is just one of the new combat-capable mounts available in the new expansion.

Melee combat is governed by runes (two each of frost, blood and unholy), which act similarly to the combo points used by Rogues and feral-spec Druids. Landing blows in melee combat generates runic power (essentially rage points) which can then be used to cast spells or inflict diseases on enemies. So imagine then a class that plays like a demented cross-breed of a Paladin, Warrior, Rogue and a Hunter, with added evil and arguably the sexiest set of starting armour in the game. And if you use the Blood Presence ability, your Death Knight can self-heal during combat, making tackling three or four mobs at a time (by yourself) a realistic proposition. Oh, and Death Knights also have a buff which allows them to walk on water, even if they're mounted. We're talking sub-zero on the coolness scale here. The Death Knight is a great addition to the class roster and its level 55 starting point will ensure that Outland doesn't become a deserted afterthought in the minds of players for some time yet, avoiding one of the key failings of the Burning Crusade release, when Azeroth was abandoned immediately following the opening of the Dark Portal.

If there are any grounds for serious criticism, it's that Blizzard has been a little conservative in terms of the quest design. There are still far too many blatant grind-quests and though there are some genuinely inspired quest chains (the Winterfin Retreat chain is fabulous, particularly the mission to rescue the absolutely adorable murloc tadpoles) with fresh feeling settings, their feel is not. Perhaps complaining about grind in an MMORPG is like complaining about the Sun setting, but a little more variety would have been nice. Another area that has agitated the WoW hardcore is the introduction of 10-man raids, which has been cited by some players as a dumbing down of the endgame content. However, given that the requirement for 25 and 40-man raids in The Burning Crusade presented a huge obstacle for casual players to make progress in the endgame, perhaps it would be wise to defer judgement on this until a larger percentage of the playing population reaches the level cap and we begin to see the long-term effects of the change.

With the release of Wrath of the Lich King, it's difficult to see how anyone will loosen World of Warcraft's stranglehold on the MMO genre. With its spectacular design, dazzling polish and ever-compulsive gameplay, World of Warcraft seems destined to remain the everyman's pick of PvE-focussed MMO for the foreseeable future, and with the implementation of new PvP mechanics, Blizzard is no doubt looking to tempt back players who jumped ship to Warhammer Online and Age of Conan as well. Time will tell whether it will succeed or not, but if Blizzard's approach to the genre over the last four years has taught us anything, it's that it plays for keeps. The competition needs to take note, because the bar just got raised that little bit higher...