History VideoGame / DoomII

** After serving as the FinalBoss of the base game, the Icon of Sin reappears at the end of Map 15 in ''Master Levels'' (titled Mephisto's Mausoleum); however, it's smaller due to the wall's size and much easier (as you're now positioned from a more convenient spot to hit its weak point directly). Also, it's no longer the FinalBoss, as that level isn't the last in the collection.

* LastLousyPoint: "Industrial Zone" has a secret teleporter that is in itself not too hard to find - though the problem arises from that it's both a teleport pad and a secret-flagged zone. To register finding the secret, you have to touch the floor of the teleport pad; trying to do so will teleport you away right before you touch the floor. It took until 2018 before somebody managed to officially "find" it (by getting a Pain Elemental to spawn a Lost Soul directly on the marine's head at the right instant, shoving him into the pad's floor ''before'' the teleport took effect). John Romero seemingly [[https://twitter.com/romero/status/1035609232501030912 confirmed on Twitter]] that this obscure method which appears to be a bug was in fact the ''intended'' solution, though [[https://youtu.be/uysh-K-HW6s?t=287 he then backtracked when asked again]], saying that the secret being unobtainable normally was a mistake they didn't catch because id had no QA team at the time. The GBA port from a decade later fixes the secret, but breaks the teleporter - an acceptable loss, considering it's just another shortcut back to the other side of the lava-river.

* DegradedBoss: The Cyberdemon and Spider Mastermind return as strong enemies, retaining their strength and HP but no longer being bosses. And in some cases, the current level may play in your favor to defeat either or both more easily. The Barons of Hell also return, but they had already been degraded after the first game's first episode (the game even adds the Hell Knights, which are weaker variants).

* AssetActor: The two secret levels are recreations of, respectively, Floors 1 and 9 from the first episode of ''VideoGame/Wolfenstein3D''. While the SS guardians make an appearance as mooks, the boss of that Episode (Hans Grosse), who should appear in the second secret level (based on Floor 9), doesn't. However, a Cyderdemon appears in his place to roleplay as him.

Relying on the same game engine as its predecessor - to the point that the first ''Doom'' received some of the second's under-the-hood changes a month prior to its full release with v1.[[NumberOfTheBeast 666]] - ''Doom II'' [[MissionPackSequel doesn't stray far from the original's gameplay]]. It was released at retail from the get-go and has levels which are played in sequence from beginning to end, unlike the shareware release of the first game and its distinct episodes. A new roster of enemies were added to increase the difficulty and force the player to come up with new strategies while traversing the game's levels. The game also features the addition of the Super Shotgun and the Megasphere, giving the player new ways to kill demons to their heart's content while keeping themselves in top form. In 2010, the game was ported to the UsefulNotes/Xbox360 through [[UsefulNotes/XboxLive Xbox LIVE Arcade]] while featuring a brand new expansion pack called ''No Rest for the Living'', which has been subsequently re-released for [=PlayStation=] 3 through the ''Doom: Classic Complete'' compilation, as part of ''[[VideoGame/Doom3 Doom 3: BFG Edition]]'', and as one of the curated add-ons for the 2019 Enhanced re-releases of the first two classic ''Doom'' games.

* AndYourRewardIsClothes: The UsefulNotes/XboxLiveArcade port offers two Avatar Awards. You'll get a Doom t-shirt for finishing the regular game, while completing the XBLA exclusive episode "No Rest For the Living" will net you a full Marine costume.

** Lost Souls do not count towards your kill percentage score at the end of a map, due to them being infinitely spawnable by Pain Elementals. So besides saving a player the hassle of having to hunt down every Lost Soul spat out by a Pain Elemental, it also safeguards against 100% kills becoming unachievable in instances where a common glitch occurs that leaves Lost Souls permanently stuck in walls after being expelled from a slain Pain Elemental. This behavior was also backported to the original game with v1.666, which was released near-concurrently with the launch of ''Doom II''. Console ports of the day are exempt from this, however, since they're built off of code compiled from v1.2 for the UsefulNotes/AtariJaguar port; ''Doom II'' ports simply added what new assets and maps their consoles could fit over the existing code rather than recompiling v1.666.

Relying on the same game engine as its predecessor - to the point that the first ''Doom'' received some of the second's under-the-hood changes a month prior to its full release with v1.[[NumberOfTheBeast 666]] - ''Doom II'' [[MissionPackSequel doesn't stray far from the original's gameplay]]. It was released at retail from the get-go and has levels which are played in sequence from beginning to end, unlike the shareware release of the first game and its distinct episodes. A new roster of enemies were added to increase the difficulty and force the player to come up with new strategies while traversing the game's levels. The game also features the addition of the Super Shotgun and the Megasphere, giving the player new ways to kill demons to their heart's content while keeping themselves in top form.

* MissionPackSequel: Aside from a handful of new enemy types and one new weapon (the Super Shotgun, which is just an upgraded version of the existing shotgun), ''Doom II'' is graphically and mechanically identical to its predecessor. Many console ports, most distinctly the [=PlayStation=] version, actually combine levels from both ''Doom'' and ''Doom II'' into one massive 50+-level game, even placing some of the new ''II'' elements into levels from the original (e.g. adding in the Super Shotgun and replacing some enemies with Hell Knights and Mancubi on higher difficulties), essentially treating the second game as a ''literal'' mission pack. The two games are so similar, and so immediately distinct from all future games in the series, that many fans often lump them together, referring to them (along with ''Master Levels for Doom II'', ''VideoGame/FinalDoom'', and more rarely ''VideoGame/Doom64'') as simply "Classic Doom".

* AIBreaker: One technical concession of the GBA port is how it sacrifices enemies' tendency to aggressively pursue the player far from their spawn points. This is a tactic you can leverage on harder difficulties to retreat to safer areas to find items.

* BloodierAndGorier: Even by playing just the censored green-blooded GBA version of the sequel, you can tell that the sequel is a tad gorier than the first game, as some of the new enemies, such as the chaingunner/heavy weapons dude and the mancubus, softly break apart with blood oozing out once you vanquish them.

* DescendingCeiling: In Level 6, if the player is playing above "Hey, Not Too Rough" difficulty, he is pitted against a Spider Mastermind that one would normally be ill-prepared to fight at this point in the game. Fortunately for the player, a switch near the elevator you get off lowers down a crushing ceiling to kill the Spider Mastermind for you. Thus, the level is appropriately named "The Crusher".

* UndergroundMonkey: The game introduces the Hell Knights, variants of the Barons of Hell that attack with a differently-colored type of projectile and have a crimson skin.

* UniqueEnemy: The secret levels based on ''[=Wolf3D=]'' have that game's blue-clad SS enemies to populate them. They're a lot less dangerous here than in their home game, so the developers throw more of them at you to help make up for your superior firepower.

* ExpansionPack: ''Master Levels for Doom II'', a collection of standalone levels produced by some popular members of the WAD community of the time (the titular "Masters"). There was also ''VideoGame/FinalDoom'', a pair of 32-level campaigns that was promoted as another expansion, but unlike ''Master Levels'', actually didn't require a copy of ''Doom II'' to work; see that game's trope page for details.

* Over100PercentCompletion: The FinalBoss, the Icon of Sin, will continuously spawn in hordes of enemies, meaning the player will likely have a kill percentage in the ''thousands''. This also happens when that boss is fought again in one of the Master Levels.

* TheVeryDefinitelyFinalDungeon: Icon of Sin, named after the FinalBoss. A giant lake of blood, a demon hundreds of feet tall, and a reverse shooting gallery with rows of monsters blasting away at ''you''.

* HelpfulMook: The rocket zombie (Revenant), introduced in this game. They tend to be more dangerous for foes than for the player due to their [[ImperialStormtrooperMarksmanshipAcademy frequency]] of [[UnfriendlyFire friendly fire]] and [[SplashDamage splash damage]].