Warning! Spoilers ahead for Moon Knight episode 3, "The Friendly Type"
Due to their Dissociative Identity Disorder (D.I.D.), Steven Grant and Marc Spector share the same body in Disney+'s Moon Knight; however, Steven seems to wield more control when alternating from one identity to the other. This is particularly interesting because Marc appears to be far more well-informed about their situation than Steven, and possesses more skills that would be helpful in their increasingly frequent high stakes altercations. Additionally, Marc Spector is the most prominent and centrally active identity of the character as originally written in the comics, making Moon Knight's choice to enter the story through the perspective of Steven Grant intriguing in its deliberate diversion from the source material.
Both played by Oscar Isaac, Steven and Marc are vastly different identities with conflicting priorities, leading to much internal debate. The Egyptian god Khonshu is another voice added to the fray in Marc and Steven's head, though he is actually a separate, superlunary entity that is using Marc as his avatar. Khonshu does not like to deal with Steven, who he refers to as "the worm." He treats Marc very differently, however, as they seem to have a history and ongoing rapport - and perhaps even some mutual respect.
Despite Khonshu's regard for Marc's strength and his dismissal of Steven as weak, it is the latter that demonstrates more power when exerting control over the body that they share. In Moon Knight episode 3, "The Friendly Type," Steven is able to take over from Marc during a fight without his explicit permission. However, Marc does not seem to be able to do the same, as shown when he has to plead and bargain with Steven for control in order to save them from the supernatural Egyptian jackal in Moon Knight episode 1. Perhaps the matter is less about which identity is stronger, and more about the firmness of their respected convictions; Steven's desperate desire for peace without violence trumps Marc's survival instincts and the secondary goals that compel him to fight. This would be consistent with DID itself, wherein specific identities can have specific roles that see them take over when under types of threat - which would allow Steven to take control of the body, but not Marc.
Throughout episode 3, during which Marc is largely at the forefront, Steven entreats him at every turn to stop fighting and to just walk away. It is during a moment like this that Steven wrests control away from Marc and defuses a hostile situation. Though Marc did not consciously give him control, it is possible that Marc secretly desires the same thing as Steven deep down: peace. Marc does not want to hurt anybody; he fights in order to fulfill his deal to become Moon Knight with Khonshu, which forces Marc to continue his life of violence and danger despite the fact that he seems to have grown weary of it. Consequently, his will to fight does not match Steven's determination to stay safe and avoid conflict.
Of the two identities, Steven is markedly more concerned with self-preservation and protection than Marc. Given Marc's penchant for perilous activities, it could be that Steven is able to override him at times for the purpose of their own survival. Since the Steven Grant identity largely takes a backseat role to Marc Spector in the comics, a definitive answer cannot be derived from the original source; therefore, the show will have to explain its own logic and rules in terms of how the identities function and how much Khonshu has to do with it at some point. Hopefully, all will be revealed as Moon Knight continues.
New episodes of Moon Knight premiere Wednesdays on Disney+.