The Mantis Claw is an Ability in Hollow Knight. It allows for clinging to walls and jumping off them.
While close to a wall while in midair, press in the direction of the wall to cling to it and slide down. Press JUMP to launch diagonally away from the wall. This can be repeated an infinite number of times, allowing the Knight to climb up walls. Can only be used on completely vertical surfaces.
If both the RIGHT and LEFT buttons are pressed while sliding down a wall, the Knight slides at normal falling speed.