The Wall of Doom is a solid, black, pyroclastic surge that destroys everything getting in its way. When it approaches, the sky turns red and everything else is seen as a silhouette, including the Doom. It was created by the huge meteor that landed in the first level of the challenge game; so one may consider the Wall of Doom as the fiery shock wave or the firestorm that was created from the impact.
The player can earn Trophies for Doom Surfing, when they stay within or alongside the Doom without dying. This is best done on Salty Flats, but it's possible to do the entire sixty second doom surf on the first level (but you
Wall of Doom
must have the game mode set to Easy, seeing as on all other difficulties the Doom clears the stage in less than sixty seconds).
The Doom is the motivating factor of the game, as the Dino (the player) has to reach the end of the level before he gets consumed by the Doom. This can be subverted with the "Goodbye Doom" cheat, which disables the doom, and with the Free Roam option in Dino Run DX. The player can then explore the level at their leisure, but they can no longer find eggs, earn DNA, or even unlock trophies. Thus, the cheat is geared towards entertainment, and not cheating.
Multiple versions of the Wall of Doom are planned to appear in the upcoming Dino Run 2, including an avalanche and a Tyrannosaurus stampede.