Boiler are a strain of Chimera that exclusively appears in Resistance: Retribution and are first referenced in an Intel Document in Resistance 2. They are exclusively mutated from human female subjects.
With most human male bodies running out and already-established Chimeran forces unable to handle the warmer climates of Africa, the Chimera instead opted to utilize the vast abundance of female bodies to create a newer variant of Chimera suited for the extreme temperatures of Africa. The resulting transformation created both the Boiler and the Hag. At least two known conversion facilities for this strain of Chimera included the ones in Bonn and the Chrysalis Lair in Paris.
Within these conversion centers, comatose women flow through the pipes, and it is stated that the women are injected and gassed, mostly whilst suffocating and submerged in water. Largely due to their relatively short transformation period, Boilers have not been trained with weaponry, instead they are utilized as offensive units, serving as suicidal units with the intent of causing chaos in Allied lines. Additionally, with their transformation, their body becomes incredibly durable, able to take nearly a full magazine from a .303 Storm Rifle, as such Maquis and British forces have targeted their extremely fragile heads, often at a distance due to their explosive volatility.
During the events of Operation Overstrike, Boilers are seen deployed throughout Western Europe. Initially encountered by Maquis mercenary James Grayson in the sewers of Rotterdam, he later encounters them extensively during his exploration of the Bonn conversion facility. By the time Allied forces begin their assault on Paris, Boilers are equipped with armor plating, allowing them to survive more shots from human forces. With the success of Operation Overstrike, most conversion facilities creating Boilers and Hags have been destroyed, however, Chimeran forces begin consolidating their remaining Boiler units and by 1952, they begin deploying them throughout Africa, allowing the main Chimeran forces to establish a foothold in the continent.
However, by 1953, most Boilers have seemingly been phased out, with a potential successor strain, the Leech having been seen in the American mainland combating SRPA military forces, and supplementing the role of the Boiler. While it is unknown why Boilers and Hags no longer appear, SRPA and Western Allied forces theorize that these variants had been exclusive to the European and African front.
Boilers attack by self-destructing while releasing a powerful kinetic wave from their heads. They have hard, leather-like skin, which is durable in gameplay, and the recommended way to kill them is to shoot them in the head with weapons with high accuracy such as the Storm Rifle and Fareye FR-1. Luckily, the Boilers' heads appear to be very fragile, and will be destroyed easily. The player can try to shoot them in the body, but they can withstand much more damage than other basic Chimera, and will take longer to kill.
- Its name might come from their psychic powers, but as the game hints, may have something to do about an incubation that is quite short and similar to actual boiling.
- The Royal Marine that appears in The Guns of Rotterdam explains what Boilers are to Grayson by mentioning "Plumbing's gone, just like a menial except under it's knickers". It is worth noting for the fact that after conversion Chimeras such as Menials and Hybrids and so forth have no genitalia (or any real noticeable gender) and despite hybrid strains of Chimera being androgynous in appearance, Boilers are noticeably female.
- It's interesting to note that boilers are not deployed on offensive engagements, and therefore have no armoured/assault variant. This, coupled with the fact they are only found in or around the facilities they are created in, one can assume they are deemed for defensive purposes as a quick way to neutralize unprepared attackers or as a suicidal last line of defense.
- Due to the fact they do not appear in Resistance 2; set two years later after Retribution, they may have been deemed ineffective and removed from Chimeran units, or as previously stated, Boilers are defensive units or exclusive to the European front. Or simply because the second conversion method has been discontinued and Boilers are no longer produced.