There's a dilemma with DLC. Release it too early and gamers complain about the dishonesty of locked-out on-disc content. Release it too late and you run the risk of everyone being long finished with the game. This is the predicament Bioware has with Leviathan.
After multiple helpings of multiplayer add-ons comes the first slice of campaign content since From Ashes, which launched with the game six months ago. Most have seen the end of Shepard's war against the Reapers. Thanks to the recent Extended Cut, some have seen several. This is a problem.
The latest DLC, a two-hour sightsee spanning three new environments and a research lab on the Citadel, where Shepard turns detective in search of towering Reaper-killing organisms called Leviathans, exists in a world where the war hasn't yet been won or lost. It's entirely incongruous. You already know the plot, and therefore anything threatening to upset it rings hollow and lacks risk.
"Leviathans are vital to the war effort!", remarks Sheppard. Well, no. You already won. There's an air of inconsequentiality to the whole thing, a bit like Titanic in space.
In turn, your choices lack weight by existing in a void, but that doesn't mean Leviathan isn't worth playing if you're heavily invested. The DLC adds Paragon and Renegade points, as well as war assets, a new shotgun and assault rifle and some minor weapon upgrades on top of a galaxy-expanding story.
Your journey starts on the Normandy. A journal entry informs you that a scientist named Dr. Bryson is conducting experiments vital to the war effort, summoning you to visit the Citadel and investigate. One cut-scene later and it's clear Bryson won't be of any help, so it's up to Shepard to pick up the pieces, scout the lab and discover the Leviathan's whereabouts.
Bryson's workplace is filled with character. Little curiosities - such as a Husk head that tracks you around the room, and a tongue-in-cheek reference to a space-based role-playing-game which was criticised by 22nd century gamers for featuring a weapon that was "overpowered" - add charm to the environment. Elsewhere, there's a Plesiosaur skeleton that Shepard jokingly calls the Loch Ness Monster (EDI curtly states the Loch Ness Monster doesn't exist).