In Matt Furie's "The Night Riders," the crab serves as a pivotal element in the adventure experienced by the nocturnal frog and rat. Specifically, the crab represents a significant obstacle or challenge that the characters encounter during their journey.
It adds suspense and excitement to their dirtbike adventure as they navigate through various landscapes from forest to bat cave to ghost town to ocean.

The crab's importance lies in its role as a formidable and memorable adversary or danger that the characters must overcome or avoid.

Its inclusion in the narrative contributes to the richness of the story's plot, offering moments of tension and excitement as the friends explore new environments and encounter unexpected challenges along the way.

Thus, the crab plays a crucial part in shaping the adventurous spirit and narrative of "The Night Riders."