Limiters are a specialist detachment of the Styx military that are usually deployed in The Deeps and during important Topsoil operations. They are known for their military skills and supposed fearlessness of anything. They first appear in Deeper and are shown as a force to be reckoned with.
The Limiters first appear in Deeper. Will and Chester watch a group of them execute a group of Coprolites and renegades. After being captured by Drake and Elliott, Drake warns that the gum Will took out of his rucksack would attract the Limiters' stalkers. Later on, Drake explains the Limiters more thoroughly to the boys. He fears that Will's presence in the Deeps, combined with the preparations for the Dominion plot, are leading to Limiters appearing in greater numbers. While on patrol with Elliott, Will comes across a patrol of Limiters and stalkers, who have just killed Coprolites and hung them on poles. They barely survive, but the whole experience causes Will to have a meltdown.
A Limiter attack then causes Will to get separated from the rest of the group. While Drake, Cal, and Elliott explore the Bunker, a battle ensues with the Limiters. When the group meets up later, Elliott tells Will that Drake was captured. They see some Limiters torturing someone on a stake, who Elliott shoots to put him out of his misery (however this was not Drake, just a Styx set-up). After a few days camp, Elliott spots Limiters on the Subterranean Sea island, and has them go on the run. While escaping on a boat, she blows up the Limiters and the island. While fleeing through the Sharps, Will, Chester, and Cal overpower and eventually kill a single Limiter. A whole patrol comes following, but is defeated when Elliott blows the cavern up. Finally, at the end of the book, some Limiter riflemen appear at the Pore with the Rebeccas and the Styx Division. In the end, they kill Cal and shoot the group into the Pore.
For failure of preventing the Rebeccas from falling into the Pore, the Old Styx has 3 Limiters strip off their gear and jump into the void. The officer commits suicide with his scythe, but the other two land on the fungal outcrops. They spot the Rebeccas' flares and meet up with the Styx twins.
Limiters, in normal duty, wear ankle-length sand and dun colored coats with a distinct rectangular camouflage. In the Deeps, they wear respirators and goggles that give them an insect-like appearance, and they also utilize the Stalker attack dogs during their patrols.
Limiters are all skilled marksmen; one might say that there is no such thing as a "Stormtrooper-aim" Limiter. In Spiral the Second Officer encounters one who had killed three Colonists with precise rifle shots to the neck. They are rarely seen in the Colony, but have military training in the Styx Citadel. Tales have been circulated among the Colonists about the ruthlessness and brutality of these soldiers, some of which are true. In the past, Tam Macaulay told Sarah Jerome that a group of Limiters operating in the Deeps once killed and ate an unfortunate renegade when their food supplies ran out. They are also proficient trackers, and are notorious for being able to move undetected by their quarry.
Although they are subservient to the ruling Styx family, they appear to have a chain of command which includes officers and a general. One such officer was seen at the beginning of Freefall to be stripped of his rank for failure by the Old Styx and committed suicide as he jumped down the Pore. Another officer was shown in the Eternal City in Closer, but was killed by Chester. The Limiter General was responsible for coordinating the fall of New Germania in Closer alongside the Rebecca Twins, and also threatened the Chancellor to ensure his cooperation.
Despite their supposed fearlessness, Limiters (and other male Styx) are shown in Spiral to be terrified by the female Styx as the Phase begins, and for good reason- during a food delivery for the growing Styx Warrior larvae and their mothers, Alex and Vane brutally kill a Limiter and begin to devour him.