Instead of using a mount, you transform into a Ghost Wolf with 20% increased Movement Speed. Basic Attacks in Ghost Wolf form cause you to lunge at your target and deal 75% bonus damage. Dealing damage, using Abilities, and channeling cancels Ghost Wolf form.
(Patch January 24, 2017) Note:Fixed several issues affecting Rehgar’s pathing while attempting to attack in Ghost Wolf form.; Becoming Rooted while attacking an enemy from maximum lunge range in Ghost Wolf form will no longer cause Rehgar to continue the lunge when the Root effect expires.; Fixed an issue causing Rehgar to become stuck in an attack animation when attempting to attack a moving Medivac Dropship while in wolf form.; Fixed an issue causing Rehgar to exit wolf form if he deals damage with a Ragnaros Blast Wave.
(Patch February 2, 2016) Note:Basic Attacks while in Ghost Wolf form now gain the effects of Feral Lunge, causing Rehgar to lunge toward the target, dealing 100% bonus damage; Casting Bloodlust no longer causes Rehgar to leave Ghost Wolf form.