When Mercus first joined the memo, he was very introverted and insisted he hated everyone. After spending some more time there, he became much more easy-going and more open with his feelings (though not entirely, he's still an introvert by most people's standards).
At 7 sweeps old, Mercus was attacked by his ex-Matesprit, which is the cause of his facial scar, tiny horns, mechanical left forearm and mechanical right hand. His arm was blown off by his own grenade that had been rigged by his Matesprit - all of the other injuries were done by her personally. Mercus has developed a fear of explosives and fire since the incident. He also tends to avoid talking about what exactly happened and when asked to tell the story, he will usually say something along the lines of, "It's stupid" or "It doesn't really matter anymore."
Mercus tends to stay quiet and can sometimes come off as harsh at times, but is generally pretty calm when there's few people around and rarely picks fights with anyone except for Verzix. He is a bit hot-headed, but hardly ever resorts to physical contact when it comes to fights and usually just yells at whoever is bothering him until they stop. Mercus tends to give up pretty easily, though, so if somebody doesn't stop irritating him after he yells at them a few times, he'll just sit down and sulk.
Despite being a bit of a brat, Mercus tries his best to be acceptant and understanding of others. Though he is slightly wary of highbloods, he is still willing to befriend them. He also seems to suffer from insomnia and often complains of headaches, and he will occasionally fall asleep in the memo depending on the amount of people present. He is more likely to sleep when the memo is busy.
Mercus is pretty content with most regulars in the memo. He used to constantly blackflirt with Tajnah, but somehow she wound up being his Matesprit. Verzix was his kismesis for a time, but they are now separated.