Can only be activated while mounted. It increases your speed slightly as long as you keep moving and instantly destroys all one-click breakable blocks you run through (like plants). Running into a 'wall'* while it is active creates a small burst of block damage (comparable to TNT, but smaller) in front of you, stops you and ends the effect. Blocks may or may not be destroyed depending on their blast resistance.
* 'Wall' in this context would be any array of blocks that you can't just run over, like land mounts do for 1 block high ledges. Fences, 2-high block walls, multiblocks, etc.
Access would be from moves that explicitly run opponents over (Flame Charge, Bulldoze, High Horsepower, etc.) - possibly also head/horn based ones (Skull Bash, Horn Drill, Iron Head, etc.) if the user has a high enough Speed stat.
Of course would need to fall under the destructive Move Skills, because grief potential is pretty high...