Characters with this skill have their outdoor tile-to-tile movement cost halved. That is, they get a "free" step every other tile, though the character must have at least 1 Action Point to act even if they are currently slated to get a free step. Movement costs in the Underground are also halved, even though this is technically an indoor location. Indoor-to-indoor movement within the same large (multi-tile) building will also be halved. This ability is always active (similar to the Divine Herald skill, Feet of the Wind).
Close combat restrictions regarding Flight are waived for the character. The Void Walker may attack Flying characters with Melee and Hand-to-Hand attacks from the ground, and may likewise attack grounded characters while Flying.