When The Elder Scrolls IV: Oblivion was finally released earlier this year, it was to critical acclaim and numerous awards including Golden Joysticks. This one game was responsible for millions of Xbox 360 and PC users shunning the outside world as they spent hundreds of hours exploring the beautiful world of Cyrodiil, completing quests, joining guilds, exploring dungeons and trying to work up enough nerve to kill a unicorn.

A few months ago, when Oblivion was finally announced for the PS3, one thing caught gamers' attentions: a brand new quest line. Bethesda soon announced that this new content would also be made available via a PC expansion pack and Xbox Live. As it happens, despite being announced as the main selling point of the PS3 version, Knights of the Nine actually debuted on those formats first.

As if the epic-ness of the main game wasn't enough, the Knights of the Nine expansion supplies another ten-hour quest line, mixing the fascinating mythology of Tamriel with the chance to be really, really good. Previous factions allowed you to specialise in magic, fighting, hunting vampires, become Champion of the Arena and a skilled thief. Despite all this variety, it was the Dark Brotherhood which set the game apart, the chance to choose to become an assassin and walk the Dark Path of the Night Mother.

Bethesda obviously felt the balance needed shifting and so introduced the Knights of the Nine, a holy order of crusading warriors who serve the Nine Divines, the pantheon of deities worshiped across Cyrodiil. Just as you once chose to murder an innocent, now you can choose to enter a sacred chapel, see how it has been defiled by dark forces and accept the call of the Nine to restore the natural order.

Unlike previous instalments and side quests where, once the patch had been downloaded or installed, a helpful note popped up informing you of an inheritance, an offer of overpriced armour or a new quest, there's no note to guide you here. Cyrodiil appears just as it always has, but there are murmurings amongst the people about a strange Prophet who expounds words of wisdom and guidance by Anvil's Chapel to Dibella. The seer soon informs you that Umaril, a sorcerer with a grudge, has charged his minions with spilling blood in places of worship devoted to the Nine.

The quest is divided into several sections, beginning with a pilgrimage around Cyrodiil to the wayshrines of each of the deities. Aided only by a parchment scroll, half the fun is finding these shrines, as markers don't actually appear on your main map. This isn't too hard; it just involves a little lateral thinking. While fast-travelling is an option, getting a horse and riding the entire way is reflective and also very beautiful. Half the fun of Oblivion has been the ability to saddle up and ride on a whim, but this is a meditative journey, a reflection of the holy quest; as your in-game avatar rides, it's easy to contemplate places previously visited as well as newly-discovered hamlets, bridges and waterfalls. The land is filled with trees covered with fiery-red leaves and on the way it is possible to run into others on the road, intent on visiting each shrine and receiving a vision of Pelinal Whitestrake, the Divine Crusader and sworn enemy of the Ayleid Sorcerer-King, Umaril.

Once this section is complete, Pelinal directs you to an abandoned priory deep in the heartlands of Cyrodiil, to the ransacked Priory of the Nine. There the spirits of the slain knights send you on the real quests to reclaim magical armor and weapons once worn and wielded by the Divine Crusader himself. Now scattered across the land, some in other dimensions entirely, these are the only things which will protect against the evil sorcerer's powers.

The visuals are as beautiful as ever, and the new quest lets you see a lot of sights.

It's obvious that, as with the original game and the various side quests like Methunes Razor, an awful lot of care and attention to detail has been put into Knights of the Nine. The new locations still manage to seem like they belong, although the two dungeons seem a little generic - even the priory, with its unique undercroft, is modelled on the same pattern used for Weynon Priory.

The Knights of the Nine does introduce a new feature: visions and transportation to otherworldly dimensions. Several of these spiritual encounters take place in mid-air above the awesome landscape of Lake Rumare and the Imperial City. This is a nice touch and looks very impressive indeed.

The puzzles, however, are ingenious. Some rely on faith, common sense or memorisation, while others require a totally different way of thnking. But as well as getting new armour, the completion of the quest also heralds new magical abilities from each of the slain knights. As well as this you get your infamy rating reduced to zero, major kudos from the populous and the chance to be a Champion of Cyrodiil (yes... uh, again).

As each piece of the Crusader's garb is recovered, NPCs begin paying attention to this little group of courageous warriors and offer to join. As Commander of the rejuvenated order, you get to choose who to accept and who to reject. When the final confrontation comes, eight will follow you into the jaws of Umaril's lair on the western coast of Cyrodiil, just north of Anvil. Then, once the quest is complete, you can pick any one from the various different races as a minion to follow you on your wanderings. Yes, this is what Oblivion is really about: the minions.

The PlayStation 3 version's big addition made it to PC and 360 first

There are some blemishes on an otherwise stunning example of downloadable content. In the original game, a small selection of actors provided the voices for all the members of a particular race. When you approach a beggar in Anvil to enquire about the mysterious Prophet, he begins talking in what is obviously a new voiceover only to revert to a completely different accent once the new information has been passed on. It's not always that obvious, but tarnishes the overall effect a little.

While Umaril remains the Big Bad of the expansion, he has his own super-powered minions known as Aurorans, who look a lot like the Daedric warriors found in Oblivion, but pack a much bigger punch. Fortunately, they also carry flawless gems, money, spells and decent weaponry, making these encounters well worth the effort. Fortunately, if you're higher than level 20 or just have the difficulty set really low, they take only a few moments to dispatch.

Given your avatar's snazzy new wardrobe, base of operations, minions and the righteous euphoria associated with being a force for good, The Knights of the Nine is well worth the 800 Microsoft points or bargain price on the PC. This quest line is the biggest yet and keeps you hooked right to the end. While the dungeons are not as big or as maze-like as the previous expansions, the chance to really explore Cyrodiil really makes this quest much more effective and allows for a greater appreciation of the graphical tweaks and new locations. Download it now!