I'm as good as dead, and if my last act is to bring you with me "Sliver", I can't imagine a better way to go!
~ Mace's last words before his death.
Special Agent Mace is one of the two main antagonists in Infinity Train Book 2: The Cracked Reflection and one of the antagonists in Book 1: The Perrenial Child episode The Chrome Car alongside his partner Agent Sieve.
He is a chrome cop with metallic armor over his body. He also wears a trenchcoat and fedora. When in the Prime World, he can wear a latex mask to hide his identity. He can use a weapon called the Sander which he can use to kill Slivers or rogue Reflections.
Special Agent Mace is a rogue Fleck that is a ruthless and serious person who is determined to kill Lake at all costs in order to keep his job as a Fleck. After his Prime died, Mace vowed to be a Fleck and keep rogue reflections from having their own individuality.
He is also shown to be a snarky and arrogant official, taunting and mocking Lake at any chance he gets to make her vulnerable, doubtful, and weak.
He also isn't afraid to kill himself if it means bringing Lake with him, even though Lake wants to be her own person. This did lead into Mace's inevitable downfall, as he was easily overpowered by Lake as his legs were crushed by the Infinity Train.
Special Agent Mace made his debut in the Book 1 episode The Chrome Car, were he and Agent Sieve are tasked with killing Lake and preventing her from going into the Prime World. They lock her prime, Tulip in the Flec car so they can hunt down Lake and "sand" her out of existence. Tulip eventually escapes and Lake jumps into Tulip's mirror, becoming her own person and escaping the Flecs.
Special Agent Mace and Agent Sieve return in Book 2 as recurring antagonists. In the episode The Black Market Car, Mace and Sieve pursue Lake in the title car though Lake eventually hides behind a magical deer named Alan Dracula in order to evade the Flecs.
Agent Mace and Sieve later appear towards the end of the episode The Map Car. After defeating Marcel, the water turns back to normal, and since the water is reflective, Mace and Sieve emerge from the water to kill Lake.
The duo appear in the follow-up episode The Toad Car were they warn a new passenger named Jesse Cosay to step away from Lake. Lake, Jesse, and Alan Dracula eventually escape the Flecs in the Toad Car were a Toad named Terrance asks the Trio to kick him. Jesse is reluctant to kick the Toad when Lake pressures him to do so. Eventually the two decide to get some rest separately. As Jesse is watching a video on him and a group of his other friends bullying his little brother Nate for failing on the man test while feeling a bit of regret for his actions, Lake questions his good persona, which causes to Jesse to rest on the train door. Sieve continues to manipulate Jesse into turning against Lake and bring her in via Jesse's smartphone as Mace prepares a heating device from the Chrome Car called "The Lawbreaker". Jesse slightly agrees with the promise that the duo don't cause harm onto Lake. Lake overhears this and breaks Jesse's phone, not wanting him to let in the Flecs though he denies that he didn't want to go through with it. Mace eventually uses the Lawbreaker to burn their way through the Toad Car. Alan Dracula eventually kicks Terrance, causing the door to open. The trio take Terrance and trap the Flecs inside the car with the plug to the Lawbreaker ripped, preventing them from pursuing the trio for now.
The duo later appear towards the end of the episode The Mall Car were a member of the Apex, Grace intentionally releases Mace and Sieve from her pocket mirror to kill Lake and Jesse. The duo pursue the trio once again, until the number on Jesse's right hand goes down to "0" causing the door to Arizona to open for them. Unfortunately, Jesse is the only one that can enter into the door and not Lake. He tries to go back for her but the portal pulls him right in before he can return, leaving Lake in the mercy of Mace and Sieve who replies "End of the line, sliver".
The duo appear in the episode The Wasteland as they continue to chase Lake and Alan Dracula. Lake uses the Apex's harpoon rope to pull Sieve into a train bridge. She tries to do the same to Mace, but he dodges it and uses the Sander to slice a part of the rope. Mace uses the rope to pull in Lake, cuffs him to her, and attempts to bring her back to the Chrome Car for execution, but one of the cars starts to move. Though Lake is able to move out of the way, Mace is not so lucky and his legs get crushed by the train wheels, leaving the trio stranded in the Wasteland. Mace is still severely injured from losing his legs as Lake has no choice but to bring him along for the journey. As Lake tries to leave the Wasteland, the force of the Train prevents the three from going any further as Mace taunts her. The trio are pursued by Ghoms and Alan Dracula uses a ball of antlers to hide them. As Lake and Agent Mace argue inside the antler ball, Lake decides to take a passenger pod to make the Conductor give her an exit. As she is running back to the barrier, one of the Ghoms touches Alan Dracula, causing him to temporarily vanish. Lake runs with Mace into the barier and jumps from the force of the barrier. Lake then uses the other half of the Harpoon Rope to climb back up the Train. Suddenly, Mace grabs onto Lake's left wrist, attempting to pull Lake down the Train's wheels with him. However, Mace's plan fails when Lake overpowers him by headbutting him and swinging with enough momentum to kick Mace into the Train's wheels, killing Mace off for good as his fedora flies into the Wasteland.
Mace is later mentioned in The Number Car as Agent Sieve plans to avenge the death of his colleague, but he eventually gets killed by Alan Dracula before he can succeed in his plan.