- "Anyone have a good day today? No? Didn't think so. Me neither. Can any of you remember your last good day? I know we have it good here in the Commonwealth... I know it's better than whatever we had before we got here. But don't you see how much better this place could be? Day after day... we sweat and toil and grind... why? Do any of you like risking your lives for Governor Milton and her friends? I thought not. So why do we let them stay in power? Their power... is us. We see them sitting on their perch, looking down on the rest of us. It doesn't have to be that way. We can install new leaders... better leaders. We could do it quickly and peacefully, we could..."
- —Mercer trying to rally to the Commonwealth Military to overthrow Pamela Milton.[src]
Little is known about Mercer's life prior to or as the outbreak began, other than he served in the U.S. Military as a Marine and was on leave before the apocalypse started.
At some point in the apocalypse, Mercer encountered a network of communities called the Commonwealth which he subsequently joined in the rank of Chief "Officer", while also acting as a personal bodyguard for the Miltons.
Mercer is watching over Sebastian who is with Kayla. Once walkers got too close to them, Mercer saves them, only for Kayla to yell and walk back to the Commonwealth and Sebastian yell at Mercer for ruining his date. Mercer is later talked down to by Sebastian's mother Pamela. Later Mercer is talking to George about over throwing Pamela, to which Siddiq overhears.
Mercer later disarms Juanita after she gets into a fight with a few officers. Sebastian wants the survivors banished for threatening him, but Mercer points out Sebastian provoked them, telling him that he can't go around slapping people for no reason. Sebastian then slaps Mercer, but is quick to retreat when he sees that he's angered the officer.
Mercer accompanies Pamela Milton on her trip to Alexandria.
This list shows the victims Mercer has killed:
- Numerous counts of zombies and unnamed people
Mercer is Sebastian's personal bodyguard and the two have a very poor relationship. Sebastian is verbally abusive to Mercer, despite Mercer saving him from numerous counts of walkers which resulted in him ruining Sebastian's date with Kayla. Mercer likewise hates Sebastian strongly, but holds his tongue when around him. Sebastian looks down on Mercer, and possibly views him as expendable.
- "Did you say loyalty? Where's your fucking sense of loyalty? I was never more than a glorified errand boy for you. I was a babysitter. I was a chauffeur. I was your whipping boy. You put me in danger more times than I can remember, and you never seemed to give a fuck all the times I nearly died for you. You're not a leader, you're a fucking wannabe queen, and I'm not waiting around until you try to install your shit-for-brains son as your replacement."
- —Mercer to Pamela upon having his loyalty questioned.[src]
In Issue 187, Mercer loses all respect for Pamela and goes as far as trying to rally the Commonwealth Military to overthrow her. When confronted by Pamela about his actions, Mercer lists all of the times he risked his life for Pamela and how she didn't care. He calls Pamela a "wannabe queen", and seems disgusted by her leadership.
Mercer and George have a good relationship and often confide in each other. They go as far as conspire to overthrow Governor Milton, though they claim they are just blowing off steam when doing so. When Mercer tries to rally the soldiers to overthrow the governor, however, George refuses to join him, though he is visibly ashamed of doing so. George ultimately does join the rebellion, and helps Mercer escape from jail, explaining that, back in the locker room, he didn't know which soldiers were loyal to them.
Mercer and Princess are on good terms. She is romantically attracted to Mercer, when he saves her from a herd of walkers she kisses him.
Later on, after arriving at the Commonwealth, Juanita and Mercer have sex. Their conversation afterwards shows they feel something for each other. Mercer mentions that he really likes listening to Juanita talk and that it's definitely not a casual thing. They kiss and Juanita says that her life is getting better every day now, to which Mercer smiles happily in response.
- "Rick Grimes... you're the leader the Commonwealth needs."
- —Mercer to Rick.[src]
Mercer and Lance were shown to have a good relationship, but it's currently strained due to Lance walking in on Mercer trying to rally the Commonwealth Military to overthrow the Governor, mentioning that Pamela will be very disappointed in him.