When Warhammer 40,000: Dawn of War came out just under four years ago it didn't revolutionise the RTS genre, but it did offer a compelling, solid, fun and, for its time, spectacular strategy experience. However, it did feel slightly lacking in the playable race department, offering only the Space Marines, Orcs, Eldar and Chaos Marines for future fantasy fans to sink their fangs into. Three expansions and nine races later we've finally got our hands on the Dark Eldar and the Sisters of Battle in what's promised to be the final Dawn of War expansion ever. Having pumped hours into the two new races, stayed up late into the night busting open the ultimately unnecessary single-player campaign meta-game and stared bleary-eyed at the game's new air units, we can confirm that Soulstorm is bloody brilliant and a fitting finale for the RTS franchise. Phew.

First off the two new races. The Dark Eldar are evil incarnate, kind of like the Eldar gone very, very bad. They concentrate on pain, torture and terrible acts of depraved violence. And they love it. And I love them for it. The Dark Eldar, while not the most popular of races among fans, are an intriguing lot. They've got a creepy, crazed feel that should offer the more unstable of Warhammer 40k fans an alternative to the similarly bad but more soulless Chaos Marines.

On the battlefield the Dark Eldar are best used with run and gun tactics - their high mobility but low durability makes them perfect for quick-fire attacks and even quicker retreats. Because of this the Dark Eldar are a very strong tier one race, but get less useful the longer a skirmish goes on. Their super-powerful Dais of Destruction is more of a spectacular luxury than a useful unit. Better to rush your opponent and try to finish them off before they pump out the Terminators.

The Dark Eldar's hook is the harvesting of souls from corpses strewn about the battlefield. Soul Essence is a spectral resource used to power their sickest and most powerful abilities, some of which affect the entire battlefield. For example, you've got the Screams of the Damned ability, which reduces the morale of all enemies, to the all encompassing Soulstorm attack itself. These special abilities are accessed from a bar above the main toolbar at the bottom of the screen, and consume souls from the Dark Eldar's Soul Essence attack, meaning you'll have to make sure you harvest as many souls as possible from the corpses of your defeated foes.

The Dark Eldar are evil incarnate

The other new playable race, the Sisters of Battle, are an all-female Space Marine/Imperial Guard hybrid who have taken their devotion to the God-Emperor a tad too far. They have an all white angelic look, with halos and Organ tanks (yes, I said organ tanks). They're good all-rounders, durable, mobile, and powerful, but they don't excel in either area. Like the Dark Eldar, the Sisters of Battle won't top many Warhammer 40k fans' favourite race list, but they're worth a few hours of play, if only to hear some of the fabulous lines of dialogue their units have been blessed with.

Unique to the Sisters is their Faith, built up by adding Holy Icons to Listening Posts. In the game Faith acts as a sort of supplementary tier, granting Act of Faith special abilities and access to the Sisters' most powerful units, but in the Dawn of War lore it is the "metaphysical measure of their devotion to the Emperor". Sounds like a dodgy cult to us.

Nothing from the Dark Eldar or the Sisters of Battle, changes the way hardened Dawn of War veterans will play the game. The fundamentally fun take and hold resource based gameplay is as important for both the new races as it is for the Space Marines, Orcs and everyone else. In a way this sums up everything you need to know about Soulstorm - it's more of the same.

Each race has been given air units, a first for the series. These work in almost exactly the same way as ground units except they can travel over all types of terrain. Most are mobile and best used in quick strike attacks. One of Soulstorm's biggest draws for fans will be messing about with their favourite race's new air unit. Unfortunately you can't control their height, which is a bit of a shame, but we understand that this could potentially have caused problems on the battlefield.

We're not fans of the campaign meta-game

While we're perfectly happy to see a refinement of what makes Dawn of War great, we don't like new features that just get in the way. We're talking about the turn-based campaign meta game that will be instantly familiar to fans of Dark Crusade. Built into Soulstorm's campaign, the meta-game focuses on requisition, taking control of some 31 territories across four planets and three moons, and fortifying strongholds as you bid to conquer the deep-lying Kaurava system. Soulstorm's story revolves around a warp storm which has attracted the attention of the game's nine races, who all want the Kaurava system, and the secret behind the warp storm, to themselves.

When you start the campaign your race already has a stronghold on one of the system's territories. During each turn you can move your forces to a nearby territory and attack (triggering a traditional, on the surface Dawn of War battle). Win the battle and you'll take over the territory and gain requisition points, to be spent on buying buildings and units that guarantee a force of some description will be immediately available should an enemy force attack you and draw you into ground combat. Each faction has a racial ability - the Dark Eldar for example can travel across the Kaurava system via Ancient Gates, while other races can only move to nearby territories. Conquer an enemy race by capturing the territory which houses their stronghold and you'll obliterate them completely and assimilate their racial powers.

The point to make about this campaign meta-game is that, while initially amusing, it quickly gets in the way of Dawn of War's traditional RTS combat. Indeed we found it became quite an annoyance pretty quickly. We suspect some gamers will love it and some will hate it, since it's effectively ended the cutscene-style single-player campaign story we loved from the original game. It may be an easy to understand and pretty cool bonus feature, but we reckon it's ended up being a hurdle through which fans are forced to jump if they want to get down to the nitty gritty RTS gameplay.

Soulstorm is a fitting finale for the Dawn of War RTS series.

We're sure that Soulstorm will be of most interest to gamers who own Dawn of War and perhaps the previous two expansions already, but RTS fans of all kinds should be interested. Soulstorm is a stand alone expansion, meaning you'll be able to use all nine races in the single-player campaign and single-player skirmishes, but if you haven't got the original game installed on your PC, and the other expansions, you'll only have access to the Dark Eldar and the Sisters of Battle in multiplayer, which is where Dawn of War excels.

The graphics look a little dated - in the four years following Dawn of War's release much better-looking RTS games have been released, including Relic's own Company of Heroes - but the unit animations still have a cool factor missing from many of its rivals. And Soulstorm, like its predecessors, does a great job of providing an intense, war-torn, battlefield for you to play with. But the most important thing is that the game is great fun, and will surely touch the soul of every RTS geek who's ever dreamt of being a Space Marine.