Salarian scientist Mordin Solus has some of Mass Effect: Legendary Edition's most memorable moments. When he isn't singing about xenobiology to the tune of a Gilbert and Sullivan classic or giving Shepard advice on the technicalities of their love life, Mordin has the potential to be at the center of some of the trilogy's dramatic, heartbreaking scenes.

Depending on the player's actions, Mordin may sacrifice himself toward the end of Mass Effect: Legendary Edition to distribute a cure for the genophage, a biological weapon used to drastically reduce the Krogan birthrate that he helped to improve. Though this doesn't happen in every playthrough of the original trilogy, there are reasons to think Mordin's sacrifice may become canon in Mass Effect 4. If it does, that decision will come with its own huge implications.

RELATED: Mass Effect: Legendary Edition's Kaidan Alenko isn't a Bad Companion, He's Just Misunderstood

The genophage was originally created centuries before humanity took to the stars. The Rachni Wars began in approximately 1 BC when several Salarian scientists reactivated a dormant Mass Relay which, unbeknownst to them, led to a system inhabited by the Rachni. It wasn't long before the scientists had been captured and their technology reverse engineered. The Rachni poured through the Mass Relay and launched an assault on Citadel Space. Given they are able to reproduce at an alarming rate, the species of the Citadel fought a bloody conflict for the following three centuries, unable to push the Rachni back.

It was only when the Salarians uplifted the Krogan, who had rendered their home-world a wasteland through a nuclear war, that the tide turned. Like the Rachni, Krogan fertility rates were extremely high. Once weaponized, the Krogan were able to fight the Rachni all the way back through the Mass Relay, exterminating what they believed to be the entire species. However, the newly uplifted Krogan weren't satisfied being the Citadel's attack dogs. The Krogan Rebellion followed the Rachni Wars, and the Citadel engineers the genophage in order to greatly reduce the Krogan population.

In Mass Effect 3, Solus can sacrifice himself to distribute a cure to the Krogan. There are reasons to think this could become canon in Mass Effect 4. The trailer for Mass Effect 4 already seems to show that the next chapter in the series will canonize some optional events from the original trilogy. There's a dead Reaper and a hint at Shepard's survival in the trailer, plus an image of a Mass Relay being rebuilt later posted by BioWare. All of this indicates that the third game's Destroy Ending will be the starting point for the next story.

If BioWare is willing to canonize the Destroy Ending, it seems likely that the genophage will also have been canonically cured thanks to Mordin's sacrifice. If so, this would have huge consequences. Though the process is likely to start slow, it seems the Krogan population could once again be on the rise by Mass Effect 4.

This could see the Krogan take on a new role. Another rebellion seems unlikely after the Reaper invasion nearly wiped out the galaxy, though that certainly didn't stop them after the Rachni Wars. It is likely, however, that the Milky Way will see the balance of power shift, especially if the Citadel Council doesn't end up reforming after the Reapers' defeat. Over the course of Mass Effect: Legendary Edition, the Council only ever had Salarian, Asari, Turian, and eventually human members. If it reforms, it's possible that the Krogan will be represented in the government to prevent another uprising. If the Citadel collapses, the Krogan may rise to the occasion and fill part of the power vacuum left behind by the Council species' as the galaxy rebuilds.

RELATED: 10 Action-Adventure Games That Have Great Stories But Weak Combat

It isn't just the Krogan who could be up to their old tricks once the genophage is cured. It's also possible that Shepard saved the Rachni species from extinction across the original Mass Effect trilogy by saving the last surviving Rachni Queen. Though both the Rachni and the Krogan could have reasons to respect Shepard, the growing numbers of both species could mean tensions are on the rise in the next game, especially among the long-lived Asari with just one generation separating them and the wars of the past millennium.

Although tensions may be on the rise, it seems likely that the Rachni and the Krogan will both be painted in a more sympathetic light in Mass Effect 4. Not only could both respect Shepard, but Mordin's sacrifice may have a considerable effect on Salarian-Krogan relations, especially if the races of the Citadel Council are looking for new allies in the wake of its collapse. The military might of the Krogan combined with the scientific genius of the Salarians could be powerful, with results depending on which members take charge.

If some player decisions are transferred to Mass Effect 4 and Mordin did not cure the genophage, it's possible that tensions may be bubbling to the surface anyway. The discovery that the genophage could have been cured - or worse, that Shepard falsely claimed the genophage was being cured in order to gain Krogan support - could leave the Krogan feeling betrayed.

Mass Effect 4 will need to find a new source of conflict after the Reaper invasion, and another cold, calculated threat like the Reapers could feel repetitive. Instead, Mordin's decisions in the original trilogy may set the stage for new conflicts to spring up between the survivors of the first three games. Just how much influence player decisions will have on the new game remains to be seen, though choices like Shepard's romances seem likely to carry over. Either way, the Krogan could be on the war march once again in Mass Effect 4, whether Mordin Solus died curing the genophage or not.

Mass Effect: Legendary Edition is available now for PC, PS4, and Xbox One.

MORE: All Mass Effect 2 Decisions That Carry Over to Mass Effect 3