A Prize Rat is any rat which is found by Lucius which manages to harm him in melee combat. In congratulations for their victory, Lucius will spare their life. He maims them before freeing them, however, to make evading him harder in the future.
Lucius' blade growled against the NorthStone pavers, spitting up sparks in its wake. Ahead of him, a scrawny figure crouched low, knife in hand and feet bloody from running bare through snow and stone. There was blood on the knife: Lucius'.
"You've evaded me, you've confounded me, and now you've drawn my blood. A wonderful chase, indeed. You're a fine rat. A prize rat."
The Rat turned to run, movements sluggish from exhaustion and hampered by the heavy helmet. Blood wept at the edges, where it dug at the neck and frayed the flesh down.
The turn was too slow, and Lucius gripped the helmet firmly by an ear.
"Let's make your next run more interesting, shall we?" Lucius said, laughing as he threw the rat against the wall hard enough for their spine to crackle. She bounced off, and the knife clattered from her hand.
She barely had time to see Lucius' sword lurch up and come whistling down, let alone evade it. The serrated teeth towards its tip chewed threw her angle and buried into the stone in a single blow, and her scream echoed high above the resonous keening of the blade's vibration.
"You may go," Lucius said, wrenching the blade from the stone with nearly the ease he'd put it there with. "Next time, you will not be able to outrun me. You will have to find other ways to survive. I look forward to meeting you again."
When Lucius strikes the Prize Rats down, he ties one of the leather bands on his arm to their helmet.