It's strange going back to fill the space boots of Commander Shepard. It's like channel-surfing onto an episode of a favourite TV show that you missed first time round. You know what's coming in the season finale, and you might not like it, but for the time-being you can content yourself with familiar riffs on well-loved material.
Leviathan is the tale of an interstellar Loch Ness Monster - a Reaper-related beast of legend rumoured to haunt darker parts of the Galaxy. A scientist hot on the creature's mythical tail is offed early doors - so it's up to Shepard and his/her chosen acolytes to piece together his research, and then trace the beastie through the Galaxy to make sure it ends up as friend rather than foe.
This equates to a lot (an awful lot) of poking around the scientist's Citadel pad, and three field trips to galactic destinations where a full cast of Cannibals, Husks, Brutes and Banshees are all keen to get back in touch with their long-lost relative.
The deep end
The action sizzles and pops in scenarios slightly askew from the norm (having you protect a repair drone MP-style for example, or deal with platforms being destroyed around you) while an engagingly sinister edge to the storyline lurks nearby. The Leviathan has a habit of using humans as puppets, and a visit to an installation full of its dead-eyed neutral-voiced slaves feels genuinely spooky.
Leviathan provides for an engaging, but ultimately unnecessary return to Mass Effect 3. It has an undeniable air of 'been there, done that, got the tropical fish', but it's undeniably pleasant to once again rub shoulders with the likes of EDI and, yes, even James Vega.
It's just a shame that such an admirable piece of Mass Effect DLC, the best so far behind Lair of the Shadow Broker, is undermined by the way the trilogy finishes. Given 'that' ending fracas it's hard to get super-passionate about Leviathan's comings and goings, especially when you (and BioWare) have mentally closed the book on Shepard's space adventures. It's a well-constructed creature chase, but not a compelling reason to return to active duty.
A satisfying, if ultimately unnecessary, monster hunt