Deathtag is a whole new approach to playing multiplayer Doom. In the past, the purpose was to have as many frags as possible.
Game play is very simple.
You must have four players to play Deathtag. Within each fort is a switch which opens a secret door in the other fort. Behind the door is a Radiation Suit. So, Deathtag requires that one player hit the switch, and that the other get the suit. Then, you make a run for the East side of the map.