Deathtag is an old gametype played before the influx of multiplayer ports like Zandronum.
You play with two teams of two, one person goes to the enemy base while the other stays at the radiation suit door. The player in the enemy base hits the switch which unlocks the radiation suit in your own base. The player who gets the radiation suit gets teleported to the enemy base, and you run all the way to the scoring line (The scoring line is 20% damage so you need radiation suit to survive)
The first team to score 5 times wins.
You can find wads in the deathmatch folder for idgames or in the first entry of the Unidoom series.