Skulltag is a port for the original Doom and Doom II by id Software.

Skulltag brings classic Doom into the 21st century, maintaining the
essence of what has made Doom great for so many years and, at the same
time, adding new features to modernize it, creating a fresh, fun new
experience.

Skulltag has no external build dependencies, but it benefits greatly from
the use of doomseeker (a server browser, *much* nicer than skulltag's
built-in server browser).

You'll also need the game data (WAD file) from one of the following:

Doom II v1.9 (DOOM2.WAD)
Ultimate Doom v1.9 (DOOM.WAD)
Final Doom: TNT Evilution v1.9 (TNT.WAD)
Final Doom: The Plutonia Experiment v1.9 (PLUTONIA.WAD)
FreeDoom >=0.6.2 (FREEDOOM.WAD, see freedoom package)
Heretic (HERETIC.WAD)
Hexen (HEXEN.WAD)
Chex Quest 3 (CHEX3.WAD)
Strife (STRIFE1.WAD)

Place the WAD file(s) in /usr/share/games/doom. The filenames can be
all lowercase (doom.wad) or all uppercase (DOOM.WAD).

Skulltag doesn't allow playing with shareware Doom, Heretic, or Hexen
data files.