This mod is part of The Vanilla Experience.
A minimalistic mod which allows skeleton horses to spawn naturally with a skeleton riding it. Whenever a skeleton spawns, it has a chance to be spawned as a rider. You can configure it to only spawn on the surface and if it should burn in daylight.
You may also be interested in Giant Spawn or Zombie Horse Spawn.
chanceSurfaceSkeletonHasHorse (default = 0.05, min 0, max 1.0): The chance a skeleton that has spawned on the surface is riding a horse.
shouldBurnSkeletonHorsesInDaylight (default = true): If enabled, burns skeleton horses when daylight shines upon them.
onlySpawnSkeletonHorsesOnSurface (default = true): If enabled, a skeleton horse with rider will only spawn on the surface.