In the competition from Episodes 104 and 105, if a player erected a full Negatower, they were automatically out of the game.
In the competition from Episodes 134 and 136, if a player found a piece of the Negatower, they had to stop digging, return to the surface, place the block, and then drink a Potion of Slowness before going back to digging. If they erected a full Negatower, they were automatically out of the game.
Jack noted that the tower looks like something out of Dead Space.
Ray was the only one to erect the Negatower in Enter the Negatower, although since he erected in the last-played round (after Gavin completed the Tower of Pimps), the elimination was rendered moot.
Gavin was the only one to erect the Negatower in Mega Dig. He found the first three blocks of Nether Quartz himself, while the final block was found by Jon Risinger, who was playing for Gavin.
In each Let's Play that the Negatower has appeared so far, one person tried to erect the Negatower (Jack in Enter the Negatower and Ray in Mega Dig) but came one block short, while someone else erected the full tower.