Titlepic: Tom Sullivan, cover of Shadows of Yog-Sothoth : a global campaign to save mankind. Chaosium, c1982. (Source file: https://images-na.ssl-images-amazon.com/images/I/81cCY333D3L.jpg )
Interpic: Tom Ardans, https://tomardans.blogspot.com/2009/11/cthulhu-in-depths.html
Credit: CRODEART, sourced from https://johnrfultz.com/2013/06/02/that-is-not-dead-historical-lovecraft/ (has a DeviantArt account here: https://www.deviantart.com/crodeart but seems to have deleted everything?! Or my scriptblocker sux)
Nightmare font: Eriance/Grey Ghost, https://www.doomworld.com/forum/topic/63615-is-there-a-text-generator-that-can-generate-quotnightmarequot-text/?tab=comments#comment-1154795

Sounds from:
RETRES.WAD (Eternal Doom resource pack, TeamTNT)
rf1024.wad (rf', original sources unclear)
hehxsounds.wad (presumably originally created by Raven Software)
TRITONII.pk3/PSX Doom (RockHardGamer 45 and BeeWen RDC, id Software/GT Interactive)
Heretic (Raven Software)
Hexen II (Raven Software)
Strife (Rogue Entertainment)
Witchaven (Capstone Software)
Silent Hill 3 (Konami)
Painkiller (People Can Fly)

(Unfortunately I didn't keep good records of which specific sound came from where... except for DSDOROPN, DSDORCLS, DSBDOPN and DSBDCLS which I remember because they were mixed together by me ie. dmdr, from Hexen II sounds. Not-WAD sounds were all sourced from https://www.sounds-resource.com/)

Palette and Colourmap from:
Screem4_DoomPal2.wad (Space Marina, https://www.doomworld.com/forum/topic/107104-screem-the-palette/?tab=comments#comment-2001259 )
(slightly modified by me)

STBAR based on ogrod.wad, cobbled together by me

Music in order of appearance:
Music Level 8 (Kileak the Blood)
11_Dark fortress.mid (Lexus Alyus)
Castlevania 64 - Silent Madness (Konami/Dooey Joon on VGMusic)
Cantara (Dead Can Dance)
Shadow of the Beast title theme (Psygnosis/David Whittaker, sequenced by Art Prawitt)
Profundo Rosso (Goblin)
D_RUNNIN (aotw.wad)
Suspense  (Bobby Prince, doom.wad)
D_OPENIN (TOON2B.wad)
Dark Halls (Bobby Prince, doom.wad, c'mon you knew that)
Music from Beyond Kadath (beydkdth.wad, from 'a free MIDI site' but Chad Noles, the wad author, doesn't say which one)
Demons on the Prey (Bobby Prince, doom.wad, you knew that too!)

Title etc. music:
D_INTROA (Bobby Prince, doom.wad)
Dimension of Dreams (Jimmy)
Sweet Little Dead Bunny (Bobby Prince, doom.wad)
nemesis2.mid (composed by Ron Hubbard/sequenced by Hyena)

Music for nitwits is (in approx. order of appearance):
Never Gonna Give You Up (Rick Astley) (gratz NaZa)
Barbie Girl (Aqua) (cheers Glen)
Wannabe (Spice Girls)
Achy Breaky Heart/Song (Billy Ray Cyrus/Weird Al Yankovic) (big ups Billy)
Yaketty Sax (Whichever misanthrope came up with Yaketty Sax)
Macarena (Los Del Rios)
Everybody (Backstreet's Back) (Backstreet Boys)
U Can't Touch This (MC Hammer)
Boom Boom Boom (The Vengaboys) (shot Vert)
How Bizarre (OMC)
AWKEN.MID (thanks Scrang. Or not)

Textures and flats from (prefixed to indicate source, except when necessary to replace animated textures/flats):
The following all sourced for Afterglow's 'Doom Textures for Level Designers' page (https://www.doomworld.com/afterglow/textures/ )
ultratex.wad (DUU_*, 40oz aka Jon Vail aka Doomer Boards Overlord)
q1tex.wad (DQ1_*, id software/Afterglow aka Derek Mac Donald)
q2tex.wad (DQ1_*, id software/Afterglow aka Derek Mac Donald)
psytex.wad (DPS_*, psyren aka J.S. Graham)
2mbrown.wad (D2M_*, compiled by Tormentor667 aka Daniel Gimmer)
ogrod.wad (DOG_*, OgrO_FiX aka François-Xavier Delmotte)
mortres.wad (DMO_*, NiGHTMARE aka Nick Baker)
nb_recol.wad (DNM_*, NiGHTMARE aka Nick Baker)
nb_flats.wad (DNF_*, NiGHTMARE aka Nick Baker)
pptex_D2.wad (DPP_*, scifista42)
 
The following from other sources as noted:
otex_1.0.wad (not renamed as per license, ukiro aka Ola Björling, https://www.doomworld.com/forum/topic/103426-otex-texture-set-%E2%80%93-update-version-10-released/ )
stalungcraeft.wad (DST_*, compiled/paletted by DooMAD, https://www.doomworld.com/forum/topic/102599-stalungcraeft-texture-pack/ )
Doomer Boards Project 16 : Cyb's Freaky Colonoscopy (D16_*, compiled by Big Ol' Billy, https://www.doomworld.com/forum/topic/109554-dbp-16-cybs-freaky-colonoscopy/ )
Doomer Boards Project 23 : Evil Egypt (D23_*, compiled by 40oz aka Jon Vail aka Doomer Boards Overlord, https://www.doomworld.com/forum/topic/114095-dbp23-evil-egypt/ )

dodgy recolours by me.
D25_* textures are edited (as in, anything that required more effort than a recolour in Slade) from a variety of sources by me.

The totally awesome TOMATULU texture is by the one and only BIG OL' BILLY! Who else?!

Enemy sprites from:
Improved pistol zombieman (The Undead Soldier/JoeyTD, https://forum.zdoom.org/viewtopic.php?f=37&t=66663&p=1128068 )
Blind Pinky (HorrorMovieGuy via Realm667, https://www.realm667.com/index.php/en/beastiary-mainmenu-136-69621/doom-style-mainmenu-105-73113#preview-22 )
Caco Lich (Vader via Realm667, https://www.realm667.com/index.php/en/beastiary-mainmenu-136-69621/doom-style-mainmenu-105-73113#preview-28 )
Vulgar (Eriance via Realm667, https://www.realm667.com/index.php/en/beastiary-mainmenu-136-69621/doom-style-mainmenu-105-73113?start=180#preview-4)
Zombie Fodder (Vader/Finalizer/Horror Movie Guy/Raven Software via Realm667, https://www.realm667.com/index.php/en/beastiary-mainmenu-136-69621/doom-style-mainmenu-105-73113?start=180#preview-12 )
Zombie Marine (Ixnatiful/id Software via Realm667, https://www.realm667.com/index.php/en/beastiary-mainmenu-136-69621/doom-style-mainmenu-105-73113?start=180#credits-14 )
Replacement Pain Elemental (temp/id Software/yuraofthehairfan/zrrion the insect/Eriance, based on the Haedexebus https://www.realm667.com/index.php/de/beastiary-mainmenu-136-69621/doom-style-mainmenu-105-73113?start=60#preview-21 )

Decorative sprites from:
MarineCorpses.wad (MDK/id Software via Realm667, https://www.realm667.com/index.php/en/prop-stop-mainmenu-163-64831/gore-a-corpses-mainmenu-167-96249?start=30#preview-9 )
GorePak1.wad (Clonehunter/id Software/LucasArts via Realm667, https://www.realm667.com/index.php/en/prop-stop-mainmenu-163-64831/gore-a-corpses-mainmenu-167-96249#preview-18 )
GorePack.wad (Captain Awesome/Monolith Productions/3D Realms via Realm667, https://www.realm667.com/index.php/en/prop-stop-mainmenu-163-64831/gore-a-corpses-mainmenu-167-96249#preview-19 )
HellTrees.pk3 (Bloax via Realm667, https://www.realm667.com/index.php/en/prop-stop-mainmenu-163-64831/vegetation-mainmenu-165-65318#preview-7)
MarbleColumns.wad (Captain Toenail, Gez, ShadesMaster, Shtbag667/id Software via Realm667, https://www.realm667.com/index.php/en/prop-stop-mainmenu-163-64831/hell-a-magic-mainmenu-168-40302#preview-18 )
MarbleBrazier.wad (Xaser, Jimmy, Minigunner, Gothic/id Software via Realm667, https://www.realm667.com/index.php/en/prop-stop-mainmenu-163-64831/light-sources-mainmenu-166-58239#preview-21 )

Any further, bad, sprite edits were by me

Special thanks to VigilantDoomer and DoomKid for their DeHackEd tutorials, there's no way I could have pulled off such a complex patch without them. Big ups also to the poster on DoomWorld who gave me the idea for a Nightmare! focused mapset, and apologies for forgetting who you are (although it was probably Nine Inch Heels now I think about it).
Last but not least, cheers to Vert for the giving the quick once over to the resources and spotting a couple errors before release.
