Percival is the only one of the main four who remembers what things were like before the outbreak. As a teen, he found Sam and saved her from what would ordinarily be a death sentence for a girl her age at the time. They formed a sibling-like bond over the years, keeping each other safe from R's or bandits intent on raiding their camps. When they heard of the legends of the Remnant spread by Ben, they both joined the rebellion. But after learning more of what Clark was like when Ben knew him, Percival lost faith in him as a leader. Now, he stays with the Remnants because he believes in their cause, but there's no love lost between him and Clark, and he makes sure the Remnant knows it.

If Lucas could be considered the group comedian, Percival is the complete opposite. As the oldest, it's always been his job to look out for others, and he's never wavered in his conviction. Always the serious one, he often grows tired of Lucas' antics, believing the latter sets a bad role model for other soldiers and that he should take his position as captain more solemnly. He carries great disdain for Clark, but begrudgingly works with him to keep the peace with Ben. Sam is his only real positive relationship, his younger 'sister' that he'd give his life for in an instant. 

His demeanor is low, sometimes even hostile, and he makes no effort to hide it. If you annoy him, one of two things might happen- either he'll tune you out, or he'll shut you up himself.