As a fan of Taleworld's equestrian centric PC game, Mount and Blade, I was a bit disappointed at the lack of offerings in the mount department of the Monster Manual. The "Charger" mount power fails to capture the inherent advantages of swinging a weapon from even a slowly moving horse and there was nothing to show for mobility powers in the two entries either. Plus, given great gulf in price between a riding horse and a warhorse, there is no cost effective way to equip hirelings other than as horse mobile but foot fighting dragoons or full-on knights. Who would spend over 700 gp for a horse archer?
So, here are stats for the three most common Middle Ages warhorses. One for budgets, one for speed and agility and one for sheer battlefield power.
The Rouncey is a general purpose warhorse for those on a budget, typically used by retainers, men-at-arms and squires. It's light, quick and well suited to being used as a riding or pack horse. It's price should be in the 200 gp to 300 gp range.
Adventure Tools file: Warhorse, Rouncey
The Courser is swift and strong warhorse prized for it's agility and is used by knights and men-at-arms. It's price should be between 500 gp and 600 gp.
Adventure Tools file: Warhorse, Courser
The Destrier is the heavy barding clad beast knights favored for head long charges into the enemy and jousts. It's strength and mass carried the day. Large, rare and expensive, these were the mounts of lords and kings. Prices should begin at 900 gp and peak at 1000 gp.
Adventure Tools file: Warhorse, Destrier