Voodoo doll

Voodoo doll is the term used when multiple "Player start" Things exist for the same player on a level. When the level is loaded, each extra player start will have a dormant "zombie" player at its coordinates. If these dormant players are damaged in any way, the actual player will suffer identical damage (hence the name "voodoo doll"). The PWAD selfdead.wad is possibly the earliest published map that contains a voodoo doll.

If the actual player has less than 100% health when a voodoo doll is encountered, and the voodoo doll is then attacked until the actual player's health is reduced to zero, then the actual player enters a strange "undead" state. The undead player can move around, but cannot select any weapons, and will die if damaged further.

In Doom Legacy, voodoo dolls do not appear, and any tricks involving them will not work. However, most source ports do not alter voodoo doll behaviour.

Instant-death teleporters
Voodoo dolls can be used for tricks in maps, most notably as "instant-death teleporters". This can be used to implement effects similar to the "bottomless pits of death" that appear in most platform games.

An example of this can be found on TNT:Evilution MAP30. At the start of this level, the player must navigate a path across a grid of platforms. Walking onto the wrong platform causes the player to teleport over a voodoo doll, killing themself.

Example
The map [[Media:Civilian.WAD|Civilian.WAD]] (file info) features two voodoo dolls to help the player achieve the undead state, and also has an "antidote" for it: taking the berserk pack, then exiting the level, will restore all normal abilities.