Pegasus

The Pegasus is an excellent raider and interceptor in any biome thanks to their high mobility combining both Speed and flight. However they can also be extremely vulnerable if cornered in a fight due to their low Health and susceptibility to Lust Damage.

Combat
In combat Pegasus quite literally fulfill the role of "Flying Cavalry", able to initiate, hit & run, fly past battle lines to strike enemy support units, intercept key enemy units with their passive SlowEffect, and finish off wounded that are trying to retreat from the frontline to heal. However their low Health means they are unlikely to survive contact with stronger enemies for more than a couple of turns if they stay engaged. That said, as they can fly you can upsize for more power without interfering with movement while exploring. In fact, having a large Pegasus is highly recommended.

Also like most Centaur species they suffer from the Bad Anatomy trait, and combined with their low Lust Resistance they can be easily lust-locked, which can be a disaster if the unit is currently behind the enemy lines with no friendly unit nearby to relieve them of their lust.

They also have no skills whatsoever to use to their advantage in battle. While this means a standard Pegasus isn't the best combat unit, it also means you're given lot of freedom to customize. As one of the few units with no skills at all, you can take full advantage of Traits like Savage and Life Bound, devote all their Mana to tanking with ShadowForm or Ethereal, or even build their entire skill set from scratch.

Lust Bound is highly recommended. Not only does it increase Mana for more tanking with Ethereal, it also prevents them becoming lust-locked. It also allows the unit to use lust for skills instead, and since they have low Lust Resistance enemies will seduce them a lot, giving them endless fuel for skill usage. Another recommendation is Burning and Heat Resistant. Not only will that make them immune to Burn and give them more damage, it will also turn them into Lava Mounts.

You can also play around with their Level Types. A Strength Level Type is a natural choice, especially if you upsize for power, but you could also consider a Magic Level Type as their Mana and Magic Growth is better than their Health and Strength Growth, giving you an extremely mobile spellcaster.

Overworld
The Land Mount ability gives them the option to carry smaller party members, reducing the time needed to traverse a land hex.

The Air Mount ability gives them the option to carry smaller party members, giving them the ability to traverse air hexes and reducing the time needed to pass through them.

They can become Lava Mounts with the Heat Resistant trait.

It's possible to start the game with a large Pegasus, which is the only way you can access an Air Mount right from the beginning. If you do that you can greatly cut down on exploration time, giving you more time to spend on other things.

Breeding
The Virility of a Pegasus, while not on the level of a purebred Centaur, is still decent, making them adequate studs.

Their Fertility is slightly better than a purebred Centaur, making them a little bit easier to impregnate.

Moneymaking
Their beauty is lower than a purebred Centaur, making them less valuable for a Brothel assignment.

Trivia

 * They are very light, so almost anyone could pick them up, enable some sexual positions that usually wouldn't be possible with a centaur like body.
 * Lore-wise the -1 to Lust Resistance and the impossibility to relive themselves of lust is justified by their inability to reach their own genitals, making them more sensitive and reliant on others.