Behemoth is a motorcycle residing in the digital world. Any Digimon who gets on him he will possess to ride him, and only release them when he finds a better rider.
Behemoth controlled a MetalKoromon to ride him, terrorizing the Forgotten Village and killing at least one Chuchidarumon. Eventually the tamers fought against him, and Guilmon jumped on his back, getting MetalKoromon off and becoming Behemoth's next rider, under his control. However Leomon knocked Guilmon off, sending Behemoth falling into the lava.
However, he later returned with Beelzemon as his rider, except Beelzemon was in complete control.
Beelzemon rode his motorcycle as transportation, but during the battle at the Land of the Sovereign, Gallantmon destroyed Behemoth with Lightning Joust.
In Runaway Locomon, Beelzemon is shown riding a similar motorcycle. It is unknown if this was a regular motorcycle or one created by the Monster Makers.