There's a bit in Asterix and Cleopatra where the Gaulic duo is introduced to Numerobis – an architect big on vision but not that great with a spirit level. Numerobis shows Asterix and Obelix houses he's built, which are all distinct but also misshapen, uneven and prone to falling apart... And though Void Shadows – the first DLC for Warhammer 40,000: Rogue Trader – is not as much of a mess as a Numerobis house, its execution is uneven enough to make for a fitting comparison.

Meant to be an odd hybrid of a more fleshed-out backstory for the base game and new content, Void Shadows takes place almost entirely aboard the rogue trader's flagship and is comprised of five new high-ranking officers, a new companion, seven shipboard locations, expanded merchant inventory, new items, two new archetypes and – naturally – a brand-spanking-new quest chain that transforms your vessel from mere (gigantic) conveyance into a bustling, breathing entity populated by (mostly) loyal crew.

As befits the Owlcats' penchant for solid storytelling and clever writing, Void Shadows is at its best while spinning its yarn. The new plot offers plenty of opportunity to roleplay and gives emotional heft, of sorts, to your ship by portraying the hardships and worries of the nameless thousands of crew who toil to ensure its continued operation.

Whether you are minding your step through the squalor of the freight line, trying to to come to grips with the morality of having a death cult roam free aboard your ship or playing detective to figure out who pumped tainted blood into your bathtub, the DLC truly shines while offering tough choices, clever plot twists and well-written dialogue.

In a neat move, the DLC can enrich a brand new playthrough (where the new officers are present from the get-go) or be experienced as late as chapter four of an existing save with equal ease (I did the latter, first, completing the whole quest chain right before speaking to Calcazar on Footfall).

The new characters are competently constructed, unique and intriguing, but occupy two distinct tiers of coherence. Some – like (obviously) your new death cult companion Kibbelah, gleefully sadistic master-at-arms Jocasta Sauerback or suspiciously chummy infernus master Einrich Monteg – have depth and feel like real individuals; while others – like the ship's new chirurgeon and confessor (whose names I pointedly cannot recall) – exist solely as two-dimensional placeholders or Convenient Plot Devices.

Voice acting is all over the place, with a few characters getting full, competent VO treatment, others being granted some spoken lines and some depending solely on text. Something I found particularly odd is that new lines for companions from the core game were left muted, leaving fresh party banter feel throwaway and unimportant: mere text bubbles of the sort you'd ignore if they originated from random NPCs.

Despite new mechanics introduced by the two new archetypes (the melee hopscotch Blade Dancer and area-of-effect Executioner) and new shipboard components (such as macro cannon ammo types and fighter bays), combat remains pretty much unchanged from the base game introducing a bit of innovation, but not to a revolutionary extent.

Locations are also a mixed bag, with some (like the dim, spooky voidship crypt or the grandiose Temple of the Bloodspun Web) offering breathtaking vistas and others resorting to more utilitarian level design or using recycled assets (like the plasma drive chamber, which you'll be experiencing for the third time).

The uneven production of the DLC is rounded out by little quality control gaffes (like enforcers hovering inside smokestacks); new bugs (mostly abilities that misfire or don't work as advertised); and the first CTD I've had since installing Rogue Trader (which I was gifted for trying to heal a wounded officer in the aftermath of a lengthy battle).

The lack of polish isn't any worse than what the base game came stock with on release, but is notable simply because Owlcat delayed Void Shadows so that they could (and I quote) "(put) everything (they) have" into "(eradicating) anything that might spoil (the player's) experience." When you go on the record saying you'll spend extra time to iron out teh kinks and still release a bit of a mess, one cannot help but comment...

At the end of the day, Void Shadows' saving grace is that where it most counts (clever writing, extensive roleplaying and plain old fun) the DLC delivers well-enough to push most shortcomings out of the limelight. If you liked the mechanics and story of the base game, its first DLC provides more of the same and won't leave you feeling shortchanged or disappointed.

If, on the other trotter, you were hoping for something innovative, awe-inspiring or buffed to a blinding sheen, well, all I can say is the second DLC (called Lex Imperialis) is slated for release "later in the year" (?) and supposedly deals with taxes... Maybe by then, the Owlcats will refine their production and deliver something truly remarkable.

Pig Notifies

• -for players experiencing Void Shadows in a pre-existing save, the Mu-Rho 79 system has two new events: one is an Explorator Fleet station, where you can trade fuel for random resources (three exchanges gave me random cargo, but the fourth provided a unique item called a Mechanicus Respirator); while the other is a large-ish space battle between pirates and the Imperial Navy, where you can choose sides (I've sided with the pirates twice, on moral grounds, which earned me a helmet called the Sniper's Bravado);