The player can customize the Praetor Suit in-game in order to advance in-game and adjust to new threats.
The suit is mostly dark green, silver, black and bronze in color, with slightly lighter legs and helmet. Both the coloration and the overall design of the suit seems to be made to resemble the original Doomguy appearance, though the Praetor Suit covers the Doom Marine's whole body, including his arms. In addition to this the Praetor Suit also appears much more technologically advanced, with a complex visor and internal systems which allows the Doom Marine to travel to Hell and return again unharmed. The suit is described as being made from nearly impenetrable material, and may be responsible for what appears to be the Doom Marine's superhuman abilities. In Doom Eternal the original Praetor Suit can be found dissasembled in his personal quarters and the interior is composed of lots and lots of wiring and large metal frames to hold the exterior armor plating
UAC REPORT FILE: HGFLTGTV
Additional relics were found in the tomb alongside the Doom Marine. Some incantation tablets, and an ancient combat suit which was given a name: the 'Praetor Suit'. When found, it was encased in an inscribed stone tomb. The suit was extracted from the rock, cleaned, and subjected to numerous tolerance tests, and found to be almost impervious to any damage. It appeared to have some mechanical function as well- small receptors on the gloves and chest plate that attracted Argent plasma and dissipated it through capillary tubes in the substructure. Markings on the armor were also consistent with images of a man (or humanoid) seen in several of the tablets and stones found on other expeditions. The same markings were also noted on the Helix Stone,
Despite it being clear that the suit can be activated in some way, no method has been found to do it. It appears to be missing a component, likely the Doom Marine himself.
The Praetor suit in-game is more than just cosmetic. The suit can be upgraded via Praetor Tokens, found on dead guards, and Argent Caches. There are also so-called Rune Trial Stones, which allow the player to do certain minigame challenges to obtain Runes. All these different collectible items allow the player to obtain certain new abilities, and increase health, suit armor and ammo capacity. The suit may also be upgraded with Delta V Jump-Boots, which allows the player to double-jump when obtained.
In Eternal, the Marine's uniform can and has been further augmented with new weapons tech designs to maximize ripping and tearing through the eldritch hordes of the Doomed. The left arm holds new ordinance known as the Doomblade, a sword of Sentinel make used for quick & grisly finishers during Glory Kills.
On top of the shoulder is mounted Equipment Launcher, adorning the upgraded suit. This device produces any manner of deploy-able secondary munitions to aid the Doom Slayer in slaying the forces of the Khan Maykr and Hell's legions. Ranging from liquid nitrogen-like freeze charges to a hyper incendiary flamethrower which yields armor drops from every torched enemy the slayer assaults. Lastly, there is the standard UAC-model frag grenade launched in an arcing motion. Doomguy's suit also sports a two way communication function which enables A.I. synergy link between his suit and the Fortress of Doom.
Through this link, the Slayer's AI partner VEGA and later Dr. Hayden can interact with the slayer via holographic projection through his helmet. VEGA can also access and bypass the advanced security locks in most UAC and ARC technologies when the need arises, giving the Slayer unfettered access to any system he comes across.
The suit was allegedly found alongside the resting Doom Marine in an ancient tomb in Hell, encased in stone. The UAC managed to extract both the Doom Marine and the Praetor Suit and bring them over to Mars. In scriptures found in Hell, the Doom Marine described as having been a very powerful man, known as the "Doom Slayer" and "Scourge of Hell" by the demons, which tried for "eons of time" to defeat the one man who they could never destroy. In the end, after having been the nightmare of even the bravest of demon lords, and having defeated the gigantic Titan, the Doom Marine was eventually captured and deprived of his suit, after which he and the suit were sealed away in a tomb so that Hell would not be destroyed.
The suit is said to have been given to the Doom Marine by an entity only referred to as "The Wretch". While the demon scriptures claim that the armor was made in hell, closer examination reveals English text and even logos for human manufactures, suggesting the armor was actually made on Earth or that the armor is of human origin and the wretch made upgrades to it.
The Armor/Suit also appears to have rusted in certain areas, suggesting the suit is in fact old, along with wear being shown as well, further supplying evidence of aging, the suit also has the number 8623, suggesting the suit was in fact mass manufactured (which would make sense if the suit was manufactured by the manufacturing plant for Marines). All depictions of the Doom Marine (in DOOM 2016) show him in the armor, it is shown in Doom Eternal that the slayer arrives in the armor from Doom 64, it is depicted that he had Sentinel armor (similar to the Marauders) at the time of his crowning.
When the Doom Slayer grabs the helmet in the introduction scene, he may have attempted to rub the Slayer's Mark off it, if not merely polish, possibly suggesting the mark wasn't there before his capture by Hell.
In Doom Eternal much of the technology used by the Night Sentinels appear reminiscent of the praetor suit. Given the existence of the Sentinel armor worn by Valen and other Sentinels (implied ot mostly be those who fought on the side of the Maykrs) one can assume the Sentinel armor served as the base for the praetor suit. It can then be assumed that "The Wretch" used human technology to upgrade the suit though why/how is still a mystery.
As mentioned there are various anomalies located on the armor, suggesting a possible Earth origin of Doom Marine's armor, despite it's purported hellish origin. Below are the anomolies:
- A Tag called D22, Possibly either referring either to the Doom Marine's soldier code or tag if he was a Marine, or a Model code for the Praetor Suit.
- The Word CAUTION under the helmet's main exhaust, An English word.
- A Production stamp (lower left of helmet)
- A Circular Icon with two circles (right arm shoulder pauldron) which could be anything from an early UAC logo, Army squad/force logo, manufacturer logo, or Night Sentinel / Argent D'Nur iconography.
- 1/0 Logistics Manufacture is mentioned on the armor several times.
- 8623 could refer to either the amount manufactured until this specific set of armor, or the date of its manufacture (i.e 8th of June 2123)
- The suit, despite having the appearance of a powered exoskeleton, provides no armor protection to Doom Slayer at the beginning of the game, and can only have 50 armor points at max without infusing with any Argent Energy Cells.
- Unlike previous games, Praetor Suit's Armor Points absorb damage completely, meaning that as long as there is Armor Points left, the player's HP won't be reduced when sustaining damage.
- The suit has appeared on numerous promotional artwork, including the Doom 2016 cover.
- The suit (or parts of it) may have been manufactured by 1/0 Logistics Manufacture, as this name is found on some places on the suit.
- The suit model is marked as "D22."
- Apart from English text, the suit also bears the Slayer's mark, also seen on the Night Sentinel holograms, associated with the Doom Marine and those who fought beside him.
- Praetor comes from the Latin Praetoriani meaning "Praetorian Guard" who were an elite group of soldiers in ancient Rome who were used as protection of the Emperor.
- The Night Sentinels which the Doom Marine was allied with, were also elite soldiers/bodyguards.
- Praetor itself was a term referring to each of two ancient Roman magistrates ranking below consul.
- The suit's helmet bears a resemblance to Quake 3 Arena's tutorial character Crash.
- Originally, the Praetor Suit was not available to players in Multiplayer, however in the fifth free update this was changed, so that maximum ranked players could equip it. It is unknown whether or not this proves that the armor was mass produced (due to how MP's lore states it to be a simulation).