The Mantis is a mechanical walking tank. It features a different weapon on each arm. The left arm carries a missile pod that can fire up to four rockets before being reloaded while the right arm carriers a turret. The player can also override the hydrolics on the Mantis which will force it to make a violent stomping motion in front of it. It is the only UNSC Vehicle in Multiplayer that only carries a single player.
During multiplayer, the Mantis is slightly dumbed down. Where in the compaign it has very powerful shields and the turret can fire for long stretches, the Mantis of multiplayer must shoot in shorter bursts and can't sustain as much fire. While this can be disheartening, a talented player can make a Mantis last an entire match by using cover and the Mantis' crouch function. Because of the shields, it is possible to sustain damage without the mech itself taking damage. When used as a support vehicle rather than on the front lines, it can easily control the flow of an entire match.
