This mod adds the Doom 1 console maps and Redemption Denied to PC Doom using vanilla assets and monsters. and includes a Sigil patch for compatibility.
UPDATE 9/5: Fixed the Sigil6 patch again.
This mod adds Hell keep, Hell Gate, Twilight Descends, The Marshes, Threshold of Pain and Redemption Denied from Ps1 Doom as a brand new episode using vanilla Doom 1 assets and Umapinfo, so ports like Prboom+2.6, DSDA-Doom, GZDoom and Doom Retro should support it.
This mod also adds a patch that adds support for Sigil that is optional, if you havent yet downloaded it you can find it on Romero.com
Once you've downloaded Sigil, go the the Rom Patcher JS website and select the Sigil6.bps patch as your patch and select SIGIL_v1_21.wad as your rom, now rename the new file you're creating to Sigil6.wad, place it in the same folder as your sourceport and the patch should apply properly.
Drag both wads onto your sourceport executable or in the same folder and create a shortcut, right click it, go to properties and add -iwad doom.wad -file Viadomus.wad Sigil6.wad to the end of the target. in GZdoom both of these files can be loaded at once with a launcher, make sure Viadomus.wad is loaded above Sigil
that is only if you want both episodes loaded, you can use a laucher to load viadomus.wad on it's own if you want
Disclaimer: keep a backup of your original Sigil wad.
Also check out my Doom 2 addon that adds The Mansion, Club Doom and expansions Here.
Fun Fact: The idea for this episode and its name is inspired by DOOD
