Center a location like people said, and do like: *Obstacle Player* brings at least 1 unit to the centered location: kill 1 zergling (or whatever) for player X at your location. You can then respawn in a variety of ways.
Off-topic: you said you were using it for a scary map. What's up with everyone making scary maps now? Before, we had House of the Haunted. Stop. Nothing more. Now we have Silent Hill, Drawn in Fear, and lots of others not worth mentioning.