Boss

In video games in general, a boss is a particularly large or difficult computer-controlled character that must be defeated at the end of a segment of a game, whether it be for a level, an episode, or the very end of the game itself.

Doom/The Ultimate Doom/Sigil

Bosses in Doom/Ultimate Doom/Sigil:

Episode	Mission	Boss
Knee-Deep in the Dead	E1M8: Phobos Anomaly	Pair of Barons of Hell
The Shores of Hell	E2M8: Tower of Babel	Cyberdemon
Inferno	E3M8: Dis	Spiderdemon
Thy Flesh Consumed	E4M8: Unto the Cruel	Spiderdemon
Sigil	E5M8: Halls of Perdition	Cyberdemon Spiderdemon

Doom II/Final Doom

Doom II and the games based on it all have the same boss:

Game	Level	Boss
Doom II: Hell on Earth	MAP30: Icon of Sin	Icon of Sin
TNT: Evilution	MAP30: Last Call
The Plutonia Experiment	MAP30: The Gateway of Hell

(MAP30: Last Call can be completed without killing the boss).

Doom 64/The Lost Levels

Bosses in Doom 64/The Lost Levels:

Mission	Boss
MAP28: The Absolution	Mother Demon
MAP39: Final Judgment	Resurrector

Heretic/Heretic: Shadow of the Serpent Riders

Bosses in Heretic/Heretic: Shadow of the Serpent Riders:

Episode	Mission	Boss
City of the Damned	E1M8: Hell's Maw	Iron Liches
Hell's Maw	E2M8: The Portals of Chaos	Maulotaurs
The Dome of D'Sparil	E3M8: D'Sparil's Keep	D'Sparil
The Ossuary	E4M8: Shattered Bridge	Iron Liches
The Stagnant Demesne	E5M8: Field of Judgement	Maulotaurs

Hexen: Beyond Heretic

Bosses in Hexen: Beyond Heretic:

Hub	Level	Boss
Shadow Wood	Hypostyle	Death Wyvern
Heresiarch's Seminary	Heresiarch's Seminary	Heresiarch
Castle of Grief	Gibbet	Heresiarch
Necropolis	Menelkir's Tomb	Menelkir
Necropolis	Traductus' Tomb	Traductus
Necropolis	Zedek's Tomb	Zedek
Necropolis	Dark Crucible	Korax

Strife: Quest for the Sigil

Bosses in Strife: Quest for The Sigil:

Mission	Boss
MAP09: Programmer's Keep	The Programmer
MAP10: New Front Base	Macil (at the player's choice of time) Macil's Spectre
MAP12: The Temple of the Oracle	The Oracle's Spectre
MAP16: Fortress: Bishop's Tower	The Bishop The Bishop's Spectre
MAP25: Catacombs: Ruined Temple	The Programmer's Spectre
MAP27: The Lab	The Loremaster The Loremaster's Spectre
MAP29: Entity's Lair	The Entity 3 Sub-Entities

Doom 3

Map	Boss
Alpha Labs Sector 4	Vagary
Delta Labs	Pair of Hell Knights
Hell	Guardian of Hell
Central Processing 2	Sabaoth
Primary Excavation: Artifact Dig	Cyberdemon

Doom 3: Resurrection of Evil

Map	Boss
Erebus - Level 2	Helltime Hunter
Erebus - Level 6	Berserk Hunter
Phobos Labs - Sector 2	Invulnerability Hunter
Hell	Maledict

Doom 3: The Lost Mission

Map	Boss
Hell	Vagary
Hell Outpost	Guardian of Hell

Doom (2016)

All bosses in Doom (2016) must be killed using a Glory Kill

Map	Boss
Lazarus Labs	Cyberdemon
The Necropolis	Hell Guards
Argent D'Nur	Spider Mastermind

Doom Eternal

Unlike in Doom (2016), Eternal has a boss that eventually becomes a normal enemy (albeit slightly nerfed compared to its boss counterparts).

Map	Boss
Doom Hunter Base	Enhanced Doom Hunters
Arc Complex	Marauder
Sentinel Prime	The Gladiator
Nekravol	Kalibas
Urdak	Khan Maykr
Final Sin	Icon of Sin

Doom Eternal: The Ancient Gods Part 1

Map	Boss
Blood Swamps	Trial of Maligog
The Holt	Seraphim

Doom Eternal: The Ancient Gods Part 2

Map	Boss
The Dark Lord	Dark Lord

Special effects

In most of the levels above, defeating the boss monster(s) causes the level to end. In E1M8: Phobos Anomaly (Doom), however, killing all of the Barons lowers all walls with tag 666. In E4M6: Against Thee Wickedly, killing the Cyberdemon causes a metal grate (four columns with tag 666) to blaze open, providing access to the exit switch.

The same function (A_BossDeath in p_enemy.c) is used in MAP07 of Doom II-based games to lower floors with tag 666 when all Mancubi have been killed, and to raise floors with tag 667 when all Arachnotrons have been killed. Similarly, in MAP32 (but using a different function), killing all the Commander Keens causes doors with tag 666 to open. Thus, these monsters can be considered bosses in the levels for which they play a special role.