List of Realities
"None of us knew what the rifts were or where they came from. But we all saw them as the same thing – power. A way for us to destroy each other more efficiently."--Gideon, cut narration
"Tchernobog's destruction opened many doors between the worlds. They can only be sealed by The One That Binds. That power lies within you. This reality will perish unless you restore it."--Ishmael, C2L9: The Underground
Other Names: This Reality
Main Article: Reality Beta
Other Names: Another Reality
Only one planet is known in Realty Beta (apart from a ringed planet seen in the sky), and that is only from brief visits by the Chosen and CabalCo. There is ruined architecture on this planet, possibly created by whatever now extinct creature the Bone Leech evolved to inhabit. The second reality may no longer be visited by people from Reality Alpha, thanks to Caleb closing the hole in the fabric of the universe and thus saving Reality Alpha from The Ancient One, and all others who would wish to invade it.
Also depicted in the fan fiction How Much Time Has Passed.
"Here you must enter this ancient place and seek out the ones within who would oppose you. The castle is extremely large and ancient, but it is said within its walls lies the gateway to the otherworld. A journey you may have to make to see that your business here is finished, once and for all."--Cryptic Passage README.TXT
Other Names: Otherworld
The final level of the original Blood expansion pack, Cryptic Passage, features a "gateway to the otherworld" which is able to be manipulated by the sought after ancient scroll. It is unclear if this is the same realm as Reality Beta, seeing how that is referred to as the "other world" in the description for the Death Shroud and Gideon's opening narration in The Nightmare Levels, or a possible canonical Reality Gamma.
Setting of: CP09: Castle (in part)
Also depicted in the final parts of the fan fiction Scroll.
"These revenants lurk just on the other side of the world of the living, crossing over only to harvest their victims. It is when they straddle this border between worlds that they are vulnerable, so time your attacks carefully. Beware their scythes, lest you be cut down in the flower of your youth."--Blood Beastiary
Other Names: Other Side
The description for the Phantasm describes them as coming from "other side of the world of the living, crossing over only to harvest their victims". This is why they appear to phase in an out of existence, differentiating when they are vulnerable to attack.
Setting of: not directly depicted
See also: References in Blood
The various easter eggs and references in both games to other popular media might suggest either a shared universe with numerous properties, or possibly more incursions from the multiverse (either caused by Tchernobog's attempts to "throw open the doors between the worlds" or the general decay caused by Caleb's neglect). The most compelling of these examples would be the inclusion of Xenomorph skulls and Predator weaponry in a secret alcove in C1L5: Steam Tunnels, marking a possible penetration from the universe of Alien vs. Predator, which Monolith Productions later explored in Alien Versus Predator 2 (2001) for Fox Interactive.
One could also speculate about the corpses of Duke Nukem or Jack Torrance found in Blood, or the existence of the Chachapoyan Fertility Idol and the flying DeLorean in C1L3: Lafayette Museum of Antiquities. Other incidental artefacts, such as the grave of Eric Draven, Jason Voorhees's mask and gloves, Freddy Krueger's hat and sweater, or Richard Kimble's prison jumpsuit, could easily just be coincidences. The various film posters and other nods seen in the games could also just indicate the existence of those pop culture staples within the games' setting.
See also: Crossovers
Designated by order of introduction. Closely adjacent or connected realities may share the same designation, despite differences in timelines.
As mentioned above, the corpse of Duke Nukem can be found in E1M4: Dark Carnival. This connection is further built up in the fan brickfilm Duke versus Caleb (2008), where Caleb and Duke duel in a shared continuity before ultimately joining forces against a giant robot. Lo Wang from Shadow Warrior is also seemingly aware of Duke's existence, commenting that one encounter in the game is "just like Duke Nukem!", which may imply awareness of other Build characters as well; the hanging corpse of Lo Wang is present in the Blood fan addon The Way of Ira - Chapter Two (2021). All the Build engine games feature nods to other franchises, with the Duke corpse in fact being a reference to the corpse of Doomguy found in Duke Nukem 3D (1996). Duke also appears in the platformer Cosmo's Cosmic Adventure (1992) as well as Bulletstorm: Full Clip Edition (2017), possibly tying those worlds together. Fan art featuring the big three Build characters is also common, though some may also feature Lenoard from Redneck Rampage (1997) as well as other first-person shooter heroes. The Blood fan add-on Trauma Therapy also features a Anubis from PowerSlave (1996), as well as portals to areas from Duke Nukem Forever (2011) and the Build inspired SiN (1998).
In the fan fiction Caleb on Cronus (2008), the world of Shogo: Mobile Armour Division (1998) is depicted as a reality parallel to the one that the Blood games are set in, with Caleb entering it briefly during an interlude in the middle of the plot of Blood II: The Chosen. This takes place just before the events of Shogo, with Caleb encountering Fallen and UCA troopers and the characters Commander Sanjuro Makabe, Lieutenant Commander Kathryn Akkaraju, and Admiral Nathaniel Akkaraju. A subsequent incursion, occuring after the events of both games, is depicted in the story Return to Cronus (2008) which crosses over with The Expanded Canon collection of Shogo fan fiction.
Blood II features promotional posters for Shogo, indicating that the game exists within that universe (it also appears as an arcade machine in Tron 2.0 and a "Shogo 2" t-shirt is seen in Project Origin), while Shogo has magazine covers asking "who is Caleb?". The Fallen also seem to speak the Cultist Language. The common title of the Armacham Technology Corporation with F.E.A.R. (2005) might also suggest a shared universe between that and Shogo, while other easter eggs might also tie things together. The grave of Hank Johnson is present in No One Lives Forever (2000), The Voice from Blood also narrates the action in Get Medieval (1998), Shogo features a toy doll in the shape of the protagonist of Claw (1997) and as described above Alien versus Predator is referenced in Blood II. The name "Gabriel" is present for separate characters in both Blood and Shogo, while the name Nathaniel appears in Claw, Shogo and Sanity: Aiken's Artifact (2000).
"Untold centuries ago the Vadrigar, the mysterious Arena Masters, constructed the Arena Eternal for their own infernal amusement. Virtually nothing is known of these beings except that they savor the carnage and clamor of battle. As such, they have stocked the arena with the greatest warriors of all time..."--Quake III Arena manual
In the fan fiction More Blood in the Arena Eternal (2001), it is depicted that Caleb was captured by the Arena Masters who manage a gladiatorial complex for their personal entrainment (the storyline from 1999's Quake III Arena) in another reality. In this arena, there are also captives from a number of id Software game realities such as that of Doom, the original Quake, as well as the Strogg reality from the later Quake games; an id multiverse is also suggested by Quake Champions (2017), as well as the background plot of Doom Eternal (2020), and statements that B.J. Blazkowicz, Billy Blaze and Doomguy make up a single family line in possibly one individual reality. In order to have abducted Caleb, the Arena Masters must have singularity technology that bypasses that of Tchernobog's binding. The fan game Bloom (2019, 2021) features a direct crossover between the worlds of Blood and Doom, Blood: Dead on Arrival (2018) mixes in Doom 64 (1997), while Ultra Crispy (2018) is designed to insert Caleb into various Doom engine IWADs. The fan add-on Trauma Therapy (2020) has levels TT10: Welcome Home! featuring Shub-Niggurath from Quake (1996) and TT11: Trauma Resolution? featuring the iconic Dopefish.
"I've been wondering [if] the person you [were] chasing through the stores was actually the real Caleb from the actual Blood universe who is now travelling to other universes with Tchernobog's power (think about a darker Dr Who type character) while RATM is set in a alternate universe.--Blood of Nightmares
Other Names: Alt-Blood
The 2007 fan add-on Rage Against the Machine appears to be set in a slightly altered retelling of the original game. RATME1M5: Green Town even features a section where you can hear another Caleb taking the fight to the Cabal. A reimagined version of the original also features in Re-Blood (2019), and possibly to a lesser extent in BloodCM (2012-2016) and other attempted recreations. Blood II: Ressurection attempted a modified retelling of Blood II, and arguably all modifications count as altered realities.