In the dark old days you had to buy 'BioWare Points' to exchange for Mass Effect DLC, sold in bundles of 800 so that if an expansion cost 1,200 points you'd have to pay for 1,600 of them and then just have 400 left over forever. To get some of the promotional items you'd either have to own other games—Dragon Age: Origins to score the blood dragon armor, for instance—or go hunting for codes on bottles of fizzy drink. If you wanted that umbra visor you went to 7-11 and bought Dr. Pepper until you found a code for it on the lid. Kids today have it easy.
Mass Effect Legendary Edition includes most of the series' DLC and nobody has to suffer through a drink that tastes like fizzy medicine to get it. Thought's been put into how the promotional gear is available, and now Shepard has to buy or research it. But not quite so much thought has gone into placing the story expansions in each game. Jump in as soon as they unlock and you'll have some odd moments—facing enemies who will then be introduced in later missions as if you've never seen them before, dealing with mechanics before they're tutorialized, wondering why your squadmates suddenly have no dialogue, and even rendering other side missions unfinishable.
Mass Effect's DLC includes some of the best parts of the series, but the way it's incorporated in the Legendary Edition is a bit of a mess. Here's how to untangle it, and which ones you should bother with.
Mass Effect 1 DLC
Bring Down the Sky
There's a huge gulf in quality between the original Mass Effect's mainline missions, sci-fi short stories you muscle through like Captain Kirk only cooler, and its side content, where you drive over mountains to find warehouses. Bring Down the Sky is an expansion created to fill that gulf, sending you on an exciting mission to stop an asteroid weaponized by batarian terrorists from colliding with a colony world. To prevent that you drive over mountains and fight through buildings that, to be fair, have more interesting layouts than the usual warehouses. Also, the story happens in actual dialogue scenes rather than those boxes of text.
When you should play it: The reward for finishing Bring Down the Sky is leveled, so if you want the best gear you should save it for late in your playthrough. There's basically no time when it makes narrative sense to bunk off the hunt for Saren to visit a random asteroid, but that's Mass Effect for you.
Mass Effect 2 DLC
Zaeed - The Price of Revenge
As if the 10 squadmates of the base game weren't enough, Mass Effect 2 threw in two extras as DLC. They're noticeably different from the others, with no recruitment missions—in veteran mercenary Zaeed's case, you have a quick chat on Omega and he immediately joins the squad. It makes having to fight through an entire office tower to recruit Thane seem a hassle by comparison, though Thane does have much more kissable lips. The other difference with the DLC squaddies is that they don't have back-and-forth dialogues when hanging out on the Normandy. They just tell stories based on which items you look at in their rooms.
On the plus side, their loyalty missions unlock straight away. Zaeed's involves liberating a refinery from his old mercenary company, and confronting the fact that he's kind of an amoral bastard. The main thing it has going for it is that voice actor Robin Sachs (who played Ethan Rayne in Buffy) does a great grizzled badass.
When you should play it: When you're on Omega to recruit Mordin and Archangel, recruit Zaeed in passing. Either do his loyalty mission as soon as you're finished on Omega to get it out of the way and unlock his inferno grenade bonus power, or save it for after Horizon when you're securing the loyalty of the rest of the crew.
Kasumi - Stolen Memory
The other DLC squadmate in Mass Effect 2 is master thief Kasumi Goto, recruited on the Citadel. Her loyalty mission involves infiltrating a party being thrown by an arms dealer she wants to steal something from, which makes for a nifty change of pace. Villain Donovan Hock's got a powerful combination of bad facial hair and a South African accent that make him seem like a 1980s action movie bad guy, which fits the vibe of Mass Effect 2 to a tee, though the mission itself is more like an Ocean's Eleven heist.
When you should play it: Talk Kasumi into joining the crew on your first visit to the Citadel. Though her loyalty mission unlocks straight away, put it off as long as you can. NPCs at the party gossip about recent events, all of which relate to other missions you've done, so wait until you've nearly finished to make the most of that. Take it on shortly before you do the Reaper IFF and trigger the endgame.
As a kind of double-pronged apology to everyone who missed the first game's Mako, and to everyone who hated driving the Mako up mountains, the Firewalker Pack gives you a replacement called the Hammerhead that controls quite differently. It's a zippy hovertank, incapable of flipping over, and the five missions in Project Firewalker are bespoke vehicle challenges. Unfortunately, you're not allowed to save progress in the Hammerhead for some reason and have to complete each mission in one go. Also it doesn't have a health bar—instead it lets you know it's been damaged by catching fire and making annoying beeping noises.
When you should play it: Give the first Firewalker assignment, Rosalie Lost, a try early on. If you enjoy flying the combustible beepmobile, that mission unlocks a whole sequence of them. If you don't enjoy it, skip the rest. At least you'll understand what all the jokes about it in Mass Effect 3 are referring to.
You'll be shocked to learn that a Cerberus scientific experiment has gone wrong in Project Overlord. The virtual intelligence codenamed Overlord has gone rampant on a research base, and it's up to you and two companions who are eerily quiet because none of the voice actors came back for this DLC to stop it. (Project Overlord gives the squadmates things to do in the background during cutscenes at least, and plays it for laughs.)
When you should play it: Project Overlord assumes you're still helping Cerberus take down the Collectors, so definitely start it before the Reaper IFF. It's also got sections where you fly the Hammerhead, which are going to be real weird if you haven't done the Firewalker mission that gives you the Hammerhead and teaches you how to fly it, so do Rosalie Lost first.
Normandy Crash Site
Originally this was one of the freebies included when you downloaded the Cerberus Network, a DLC authenticator and shop that could not have been given a more ominous name (Zaeed and Firewalker were free too). Normandy Crash Site is a chance to say goodbye to the original Normandy by exploring its ruins, a collectible hunt that sets off some flashbacks of the original ship and her crew. The Legendary Edition leaves these still images as they originally were, meaning they show the first game's pre-remaster graphics for an additional layer of nostalgia.
When you should play it: This one fits anywhere. Whenever you feel like finding out what happened to Navigator Pressley, or looking at the Mako one last time.
Lair of the Shadow Broker
The most substantial Mass Effect 2 expansion reunites you with Liara, now an information broker, as she tries to rescue one of her agents from the Shadow Broker. If you romanced Liara in the first Mass Effect this is your opportunity to pick up where you left off, but even if you didn't Lair of the Shadow Broker is still a blast—an opportunity to play Gal Friday while your former sidekick has a turn at being protagonist. It's got a diverse collection of fun setpieces too. There's a crime scene investigation, a fight up the side of a big space thing, and a car chase where you finally get to pilot one of those skycars.
When you should play it: When you talk to Liara on Ilium there's a dialogue option that says, "Let's get the Shadow Broker." Choosing that will start the DLC but also end Liara's chain of sidequests from the base game. Instead, complete the missions where she sends you off to hack terminals (Systems Hacking and The Observer), which are designed to give you something to do while you're exploring the hub to recruit Thane and Samara and do Miranda's loyalty mission. Wait until after you've done all that to return to Liara and start Lair of the Shadow Broker.
A bridging DLC intended to set up Mass Effect 3, this one has Shepard infiltrate a batarian base to rescue an Alliance agent, and ends with a tease of what's coming in Mass Effect 3. There's a lot of combat, some light puzzle-solving, and several moments where it frustratingly takes away your agency. You get captured whether you defeat an ambush or not, you fail to save people whether you try to warn them or not, and then the big moral choice Arrival ends on is taken out of your hands.
When you should play it: Don't bother. Nothing Arrival does turns out to be necessary to set up Mass Effect 3. If you're a completionist who wants every single possible war asset though, save Arrival until after the suicide mission. Just ignore that email Admiral Hackett sends about an urgent solo mission.
The best Mass Effect 2 DLC
Lair of the Shadow Broker isn't just the best DLC for Mass Effect 2, it's the best part of the whole game—even counting the suicide mission. Of the others, Kasumi's Stolen Memory mission is a highlight, and it's worth doing Zaeed's Price of Revenge mainly to guarantee he returns in Mass Effect 3. Project Overlord is solid too, taking some cliched elements but using them to build to a powerful climax.
Mass Effect 3 DLC
There's only one DLC squadmate in Mass Effect 3, but wow is he an important one. Not having access to Javik, or the recruitment mission where you revisit Eden Prime where it all started back in the first game, makes Mass Effect 3 feel incomplete. Heck, it's almost like From Ashes was always intended to be a part of the finished product but was held back so it could be sold for a few extra dollars—sorry, BioWare Points. Who could imagine such a thing?
When you should play it: As soon as you can. It'll be ready and waiting when you gain control of the Normandy after leaving the Citadel, though if you want to go to Palaven and find Garrus as quickly as possible I wouldn't blame you. That charming turian does have a lovely voice.
If you like deep dives into galactic history as well as deep dives into literal water then Leviathan is for you. It's a multi-part jaunt around space in search of the origins of the Reapers that climaxes on an ocean planet, and should satisfy both people who read every single codex entry and people who like seeing Shepard survive against the odds and shoot a heck of a lot of bad, bad people. Because it has both.
When you should play it: Since Leviathan has banshees in it, save it until after Kallini: Ardat-Yakshi Monastery, the mission that introduces them. To start Leviathan, when you dock at the Citadel choose Dr. Bryden's Lab instead of Alliance Docks.
Omega brings back Aria T'Loak, the asari pirate queen voiced by Carrie-Anne Moss with her own asteroid-based hive of scum and villainy. This DLC was what the B-team at BioWare Montreal worked on after finishing the multiplayer mode and before being handed Mass Effect Andromeda, and looking back it was a sign of things to come: a whole lot of thoroughly decent combat and almost none of the character-writing people play BioWare RPGs for. You help Aria take back that asteroid from the Cerberus officer who stole it from her, a villain so cliche he's got a Russian name and a thing for chess, and Aria suddenly becomes inept and kind of contemptible. It's bad, hey.
When you should play it: Omega's the one Mass Effect 3 DLC worth skipping unless you're real hard up for war assets, or you want the overpowered flare ability you earn at the end. It's a long slog you can't take a break from to do other missions, however. If you bother with Omega, wait until you've finished Aria's assignment to put together a mercenary fleet, then select Dock 42 instead of Alliance Docks next time you land on the Citadel.
The Extended Cut DLC was BioWare's official apology for Mass Effect 3's ending, and is included in the Legendary Edition. But the Citadel expansion really made up for it by returning to what the series was best at, and what Mass Effect 2 especially delivered on. It's half buddy-movie setpieces, including a fight through a French sushi restaurant and an undercover casino heist, and half fanservice.
The Normandy's crew are given shore leave and you're given an apartment on the Citadel, and after you survive yet another attack you get to explore a new hub where all the best NPCs hang out. You find out what they do with their downtime, which is mainly "get into quirky Yakuza sidequests". It ends with an indulgent party sequence where you invite your favorite characters and spend a night seeing them interact with each other as they trash your apartment.
When you should play it: There are two schools of thought about this. One says to play Citadel where it makes the most sense—right before Priority: Thessia, which is before the plot ramps up and a holiday stops feeling appropriate, and after you've done the missions that complete former companions' arcs so you can invite them to the party. The other says to save Citadel until after finishing Mass Effect 3, going back to the point-of-no-return autosave and treating it as a flashback so you can wash out the taste of the finale with this better ending.
The best Mass Effect 3 DLC
It's Citadel, a lavish demonstration of everything that's great about Mass Effect. Citadel isn't just the best DLC BioWare has made, it's probably the best thing the studio's name has ever been on and a reason to play the series by itself. Leviathan and From Ashes are quality too, and the story does make a bit more sense with them included.