The invulnerability is a powerup that makes the player generally impervious to damage. The player is not protected from telefrags, and will still recoil from a successful attack. The powerup looks like a green sphere with a grinning red-eyed head inside. While it is active in Doom and Doom II, the colors in the player's view change to inverse monochrome (with the exception of the sky, which remains unchanged), and the eyes of the status bar face glow yellow (STFGOD0), making them look similar to the demon's. The inverted monochrome display makes the game effectively fully bright, and the player will be able to see every detail even in the darkest areas. Spectres in particular become much more visible under its effects. In Doom 64, where the powerup looks extremely similar minus the red eyes, the effect on the other hand causes a brightness filter to be applied to the screen, allowing the environments and actors to largely preserve their colors.
Invulnerability lasts for 30 seconds; in the last few seconds the display will begin blinking back to its original colors. Picking up an invulnerability before a previous one has expired resets the duration to 30 seconds.
Invulnerability can also be activated with the cheat code idbeholdv.
Invulnerabilities are included in the items percentage displayed at the end of each level.
According to the function P_DamageMobj in p_inter.c, invulnerability only protects the player from attacks doing less than 1000 points of damage; while no monster in the game can do nearly that much damage in one attack, a telefrag inflicts 10000 points (and indeed will kill even an otherwise invulnerable player). This also means that DeHackEd can be used to circumvent the invulnerability powerup by creating incredibly powerful weapons.
|Thing type||2022 (decimal), 7E6 (hex)|
|Enum||MT_INV (56) - Doom|
MT_ITEM_INVULSPHERE (63) - Doom 64
|Appears in||Doom/Ultimate Doom|
Doom II/Final Doom
Doom 64/Lost Levels
|Frames||4 [ABCD] - Doom|
6 [ABCDCB] - Doom 64
|Flags list|| 0: Can be picked up|
23: Affects item %
The IWADs contain the following numbers of invulnerabilities per skill level:
- The grinning face inside the sphere appears to be derived from the lost soul sprite in Doom 0.4. Oddly enough, the invulnerability sphere in that version of the game was invisible and had an unused sprite in the IWAD which looked like a giant health bonus.
- Due to a limitation of the engine, the invulnerability artifact lights up all the areas in the game similar to the light amplification visor. Otherwise it would require an entire table of 32 shades for a proper effect.
- Doom 4-2 Alpha at toastytech.com
- alt.games.doom post about creating weapons that can kill invulnerable players, via Google Groups
- rec.games.computer.doom.editing post about creating weapons that can kill invulnerable players, via Google Groups
|Items from Doom, Doom II and Doom 64|
|Health:||Health bonus • Stimpack • Medikit|
|Armor:||Armor bonus • Armor • Megaarmor|
|Powerups:||Berserk • Computer area map • Invulnerability • Light amplification visor • Megasphere • Partial invisibility • Radiation shielding suit • Supercharge|
|Keys:||Keycard • Skull key • Demon Key|
|Weapons:||Fist • Chainsaw • Pistol • Shotgun • Super shotgun • Chaingun • Rocket launcher • Plasma gun • BFG9000 • Unmaker|
|Ammo:||Backpack • Clip • 4 shotgun shells • Rocket • Energy cell • Box of bullets • Box of shotgun shells • Box of rockets • Energy cell pack|