BioWare’s popular science-fiction series, Mass Effect, has undoubtedly shaped the gaming world ever since it first released in 2007. It doesn’t always take the traditional approach to gaming, with a boss at the end of every major mission, so the boss fights that do appear are expertly crafted.

The fights are also incredibly diverse — one is never like another, and the player could be fighting an alien with a huge physical advantage, a creature a hundred times their size, a biotic with special long-range abilities, or even themselves. These ten boss fights are the absolute best that this universe has to offer.

10 Shepard’s Clone

The Mass Effect: Citadel DLC is arguably one of the best add-ons to the Mass Effect series. It was the last DLC released for the original trilogy and opened up new parts of the Citadel station to explore.

A conspiracy targets Commander Shepard and the player must uncover the truth behind the identity theft. By the end of the DLC, they’ve discovered that a clone of Shepard has been running around that was created by Cerberus before Shepard’s revival. Players fight to stop the clone from stealing the Normandy out from under their nose.

9 Shadow Broker

The Shadow Broker is a mysterious character in the Mass Effect universe. He trades in information rather than material goods and is careful to never give out enough information for a customer to have a significant advantage; they always keep coming back for more.

In The Lair Of The Shadow Broker Mission, Shepard and Liara break into his intel centre and confront him. It’s a tough fight, especially because Liara and the Commander have to beat him on their own.

8 Tela Vasir

Vasir is a spectre, which is the job that Shepard held in the first Mass Effect. As a result, when the player is trying to find Liara (who’s gone missing), they’re inclined to trust her. After all, she has a great career record — she’s known for dissolving a slave-trading ring in a Salarian colony and investigating the theft of galactic economic intel.

However, when Liara reveals that Vasir tried to kill her, the pair must chase her down across Illium. Vasir admits that she’s been doing favours for the Shadow Broker in exchange for his information that has ensured stability — and claims that Shepard’s partnership with Cerberus is just as bad or worse than her own sins.

7 Eos Architect

Mass Effect: Andromeda players can hardly forget the first time they encountered an Architect. The one on Eos is the first of five architects that players must take on in the game.

It has a number of different offensive and defensive capabilities, so Ryder has to stay on their toes to take it down. This mechanical beast can create smaller Remnant units to swarm the team and its armour makes it impervious to ground fire. When the player finally manages to take it out, it retreats to the planet’s orbit and goes into standby mode.

6 Thresher Maw

The Thresher Maw battle is part of Grunt’s companion story during Mass Effect 2. Grunt was grown in a tube unnaturally but wants to connect with other Krogans. To do this, he and the player visit the Krogan homeworld, Tuchanka.

There, either Wrex or his brother will greet them as the new leader of his clan, and agree to have Grunt go through his people’s coming-0f-age ritual. This involves surviving the attacks of a massive Thresher Maw nearby. Technically, Shepard doesn’t have to kill the Maw — only survive for a set time — but taking it out earns a special kind of satisfaction.

5 Kai Leng

Kai Leng is a Cerberus assassin who is sent against Shepard when the player gets on the organization’s bad side in Mass Effect 3. The pair clash more than once over the course of the game, until their final showdown at Cerberus headquarters on Cronos Station. As Shepard rifles through the Illusive Man’s office, Kai Leng takes the team by surprise.

The ensuing combat is hectic, since the player must fight against Leng as well as Assault Troopers, Phantoms, and Nemeses he summons periodically. Eventually, though, he succumbs to the attacks and makes one last-ditch effort to sneak up on Shepard, which the player catches easily before finally killing him.

4 Reaper (Priority Rannoch)

The Reapers appear in huge numbers during Mass Effect 3, but the mission on Rannoch allows the player to take on just one. Shepard is attempting to use a prototype targeting laser on a Reaper base that controls Geth.

As the squad makes a break for it, Shepard stays behind to take down the Reaper that’s emerged from the base. The player must use the targeting device to call down orbital strikes on this monster — and even gets the opportunity to talk to it, afterwards.

3 Matriarch Benezia

Matriarch Benezia is one of Liara’s two Asari mothers; she was the only mother that Liara knew about growing up. As a Matriarch, Benezia had an active, public, political life, and Liara hated being in the spotlight in such a way. Choosing to study archaeology was a path to escape this pressure.

When Shepard meets Liara in the first game, she hasn’t spoken to her mother in years. In that time, Benezia joined Saren’s evil scheme, and became indoctrinated by the Reaper just like him. Shepard must fight her in an emotional mission on Noveria, but gets a chance to speak with an unindoctrinated piece of the Matriarch that she was able to keep sane using her mental and biotic prowess.

2 Human Reaper Larva

The Human-Reaper Larva is the final boss of Mass Effect 2. The Collectors have been creating it, under Harbinger’s orders, by abducting humans, breaking them down to their genetic material, and using that material to build this monstrosity.

At first, it seems inactive, and Shepard causes it to fall into ruins — until it begins to climb up and fight back. At this point, the player has to take it for real. Horrifically (and hilariously), the team behind the game nicknamed it “Baby” during development.

1 Saren

Saren was the main antagonist of the first game, and his villainy was hard to replicate in the rest of the trilogy. The final boss fight where Shepard takes him on is practically indescribable; it’s built up over a long sequence of fighting your way through the Citadel to reach him, and when you finally do, and realize that he’s truly gone mad, emotions of anger and pity rise up in your chest.

Whether players empathized with Saren or couldn’t excuse his actions, everyone agreed that his final fight was one to remember.

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