The Four Horsemen can be difficult to defeat. Use a Vah Shir Berserker with a high Summon Throwing Axe spell and a decent melee weapon and armor. When the battle starts with each horseman, run as close to them as possible. When you get close enough, their horse will stand on two feet and try to knock you down. When this happens, run around them. When the horse is on all four, hit it with your strongest melee weapon. After a while of taking a beating, the horse will leave. Next, you must defeat the rider. Each rider has a different spell. To defeat the riders, run around and throw your throwing axes at them. This will take awhile. If you run out axes, use the spell Summon Throwing Axe. You can use mana potions, just not health. If run out of mana potions, run around until your mana regenerates. An easy way to know if the rider is about to use his spell is when he lets out a loud scream. It is a good idea to use a Vah shir Berserker at level 10 or higher. By using a Berserker, you will not have to use a single potion unless you get hit bad. Remember, in order to win the challenge you are only allowed to use no more than four health potions.