4Doomsday.pk3 is a collection of selected maps which replace E1M1 to E1M8 of Doom.
Here are the authors of the eight maps:

E1M1 - A house themed map by Guy M. Babin "GhostGuy"
E1M2 - A small fortress map by Guy M. Babin "GhostGuy"
E1M3 - Originally WASE2.WAD by Walter "Daimon" Confalonieri, titled "Petersen Station"
E1M4 - Originally UNDERG.WAD by Nick Bousman "Singe", titled "Underground Maelstrom"
E1M5 - Originally PAGBSP3.WAD by Pedro Arturo Gomez Blanco, titled "Perfected Hatred"
E1M6 - Originally MPBASE.WAD by Maarten Pinxten, titled "MPBASE"
E1M7 - Originally AUXBASE.WAD by Agtronic, titled "Auxiliary Base"
E1M8 - Originally AMOK11T.WAD by David L. Davis, titled "DOOMED to Run Amok v1.1"



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