Mass Effect 4 has to be one of the most highly sought-after titles currently in development. Fans of BioWare's much-lauded science fiction series have been on tenterhooks over the fourth iteration of the epic franchise, which has promised new alien races and giant planets. The developer has remained tight-lipped over the setting and characters of the series, aside from promising that the title will not involve itself with Commander Shepard's story.

This has led to plenty of speculation from within the gaming community, particularly with regards to which characters may have a return to the series. After all, the Mass Effect trilogy was chock full of interesting squad members, with complex relationships and in-depth, nuanced backstories to discover. Here's our pick of the ten best Mass Effect squad members.

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10. Legion

Appearing late in Mass Effect 2, Legion is found by Commander Shepard in a Reaper hulk. Appearing as a Geth sniper, Legion aides Shepard and the Normandy team on their mission, but is cut down by an overwhelming force of husks. After making the decision to bring the fallen Geth aboard after completing the mission, players can use Legion for assistance in combat through the use of combat drones.

Perhaps Legion's most interesting role, however, was to provide a different - and needed - view on Mass Effect's galaxy and the role of the Geth. Initially seen as a dangerous enemy to overcome, Legion adds a level of complexity to the galaxy's factions. Not only that, but the sentient being, and his search for a soul, gives one of the strongest examples of empathy in the entire trilogy.

9. Grunt

Another character seemingly unique to the galaxy, Grunt is also picked up during Shepard's Mass Effect 2 travels. The Krogan berserker is the ultimate test tube baby, a genetically-engineered super-soldier that was supposed to combine the most fearsome elements of the Krogan race into one being. Shepard discovers the Krogan warrior still in his tube, and decides to let Grunt loose.

The berserker does not have much by way of tactical discipline, and cuts a mean and angry figure in the Mass Effect series. Nevertheless, Grunt is a powerful tank-like squad member, useful as a heavy-hitting warrior that only the foolhardy would try to fight.

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8. Jack

Jack is one of the most divisive figures within the Mass Effect series, with a personal history full of turmoil and betrayal. Abducted and experimented upon as a child, she holds a vicious anger against the shady Cerberus group responsible for her past. A talented biotic, Jack can more than hold her own on the battlefield, and is capable of cutting through wave after wave of enemies.

Beneath the abrasive exterior, however, lies a much more subtle character to find. Jack is cursed with post-traumatic stress and survivor's guilt, having suffered through the Cerberus experiments that took the lives of many of her friends. Providing an awful warning about the horrors that Cerberus could keep under wraps, Jack shows exactly how important trust is in a dangerous galaxy.

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7. Miranda Lawson

Initially cold and calculating, Miranda is introduced as an untrustworthy Cerberus operative in Mass Effect 2, watching over Commander Shepard's actions. Genetically engineered as a perfect human, she - at first - appears to be more than a little cocky. Based on her combat abilities, her attitude seems more than accurate, as Miranda is capable of unleashing devastating biotic attacks.

Before long, however, players will come to realize that there is more to Miranda than that surface pragmatic attitude. She proves to be fiercely loyal to her sister, defending her from the clutches of her megalomaniacal father. Miranda also proves to have a loyalty to Shepard and the crew of the Normandy, and is an important squad member during Mass Effect 2's suicide mission.

6. Thane Krios

Serving as one of the most tragic characters from the original Mass Effect trilogy, Thane Krios is one of the most dangerous assassins in the galaxy. Beneath the fearsome reputation, however, lies a character of spirituality, intent on making amends for a life filled with regret. Sombre and calm, Thane provides a good balance to the fury of Grunt and Jack.

Thane plays a much more reduced role in Mass Effect 3, however. The drell assassin is suffering severely from Kepral's Syndrome, a disease which is now in its final, fatal, stages. Stuck on the citadel under medical care, Thane still manages to play a vital role in the proceedings of the Mass Effect trilogy's finale.

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5. Mordin Solus

Salarian scientist Mordin has one of the most interesting stories in the entirety of the Mass Effect series, and one which is integral to the history of BioWare's entire universe. The geneticist was once part of a team researching the Krogan genophage, a biological weapon used to curb the reproduction rates of the species. Discovering that the Krogan were becoming resistant to the genophage, Mordin and his team modified the weapon to continue its effect.

In spite of this dark past, Mordin is a cheerful, chatty, character, offering up plenty of humor aboard the Normandy. First appearing in Mass Effect 2, the Salarian brings a great level of depth and character to the  series, as well as playing an integral role in the trilogy as a whole. When you mix in Mordin's neural shock attack, the scientist can also become a vital part of Commander Shepard's squad.

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4. Urdnot Wrex

Wrex is another character whose history is tied to the effects of the genophage. The Krogan first appears in the original Mass Effect as a bounty hunter and mercenary, but is secretly an extremely powerful Krogan Battlemaster. Capable of deadly heavy weapon attacks combined with biotic abilities, Wrex provides players with one of Mass Effect's most dangerous squad members.

Rough around the edges, the Krogan is certainly not one to be trifled with. However, Wrex actually provides a fantastic starting point for players to learn more about the Krogans and the genophage. Determined to save his people, Wrex commands respect and is an invaluable ally throughout Shepard's fight against the Reapers.

3. Liara T'Soni

Although Liara first appears as a naive scientist, the Asari researcher becomes one of the toughest and most fearsome characters in Mass Effect. Alongside the rest of the devastating events of the series, Liara also has to deal with a particularly horrible mother in Matriarch Benezia. By the time that Mass Effect 3 rolls around, she has even become the mysterious Shadow Broker.

Liara is one of the most important characters in the Mass Effect trilogy, and not only because of her role in the franchise's story. A purely biotic character, Liara is one that has to be managed carefully in battle. But, with the right support, the Asari can easily defeat wave after wave of deadly opponents with a number of extremely powerful warp attacks.

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2. Tali'Zorah nar Rayya

Another character that needs to be managed carefully, but to great effect, is Tali. The Quarian may appear frail at first, but Tali gives Shepard a vital defensive back line in combat, stopping large groups of enemies in their tracks. Her role, however, is much more important than her actions in combat.

The electronics expect is travelling away from the Quarian migrant fleet, taking part in a ritualistic pilgrimage. When meeting with Commander Shepard, Tali gives the player not only a highly useful insight into the inscrutable alien race, but also provides one of the more touching Mass Effect romance options. Through her attachment to Shepard and the entire Normandy crew, Tali shows exactly how important the role of the multitude of alien races is to the survival of biological life in the galaxy.

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1. Garrus Vakarian

In spite of some tough opposition, Garrus Vakarian is undoubtedly top dog when it comes to Mass Effect squad members. The Turian was initially a C-Sec operative in the first Mass Effect, charged with investigating the rogue Spectre Saren. Told to stop his inquiries into the renegade, Garrus instead teams up with Commander Shepard.

From then on, Garrus became a vital part of the player's team, in particular due to his ability with sniper rifles. Aside from his stint as the Punisher-esque 'Archangel' at the beginning of Mass Effect 2, Garrus is an ever-present part of Commander Shepard's team, a trusted confidant and fearsome combatant. Quite simply, Garrus is a must-have squad member, willing to stick to Shepard's mission to the very end. There are plenty of things that Mass Effect 4 needs to deliver, and having characters as iconic as Garrus is just as essential.

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So there we have it - our favorite squad members to aide in Commander Shepard's quest. It remains to be seen whether any of the above will feature in Mass Effect 4, but here's hoping that at least some of Commander Shepard's strong supporting cast will have a triumphant return in some way. After all, much of the strength of the Mass Effect series is built on its strong, recurring characters.

What did you make of our list? Were there any squad members you would have included? Let us know in the comments below!