"A potion to enhance a mount's potential; only strong mounts can withstand the side effects. Mounts with +75% movement speed and above will gain an extra 5% movement speed."
Go find a mount dealer! He must have mount enchantments available to sell. Speak with Lime the Sprite of Angoya Island for Item Mall mount enchantments. Keep in mind that enchantments can't be used with timed-countdown mounts!