From Pathfinder Society Scenario #2-11: The Pathfinder Trials, which isn't enabled.

Brittle Skeletal Horse

CREATURE 1

UNCOMMON LARGE EVIL MINDLESS SKELETON UNDEAD UNHOLY

Variant skeletal horse

Skeletal horses are sometimes used as mounts by other undead or monsters.

Made from bones held together by foul necromancy, skeletons are among the most common types of undead, found haunting old dungeons and forgotten cemeteries.

Perception +6; darkvision

Skills Acrobatics +5, Athletics +7

Str +5, Dex +3, Con +2, Int -5, Wis +2, Cha +0

AC 14; Fort +4, Ref +7, Will +6

HP 23, void healing; Immunities bleed, death effects, disease, paralyzed, poison, unconscious; Resistances cold 5, electricity 5, fire 5, piercing 5, slashing 5

Void Healing

A creature with void healing draws health from void energy rather than vitality energy. It is damaged by vitality damage and is not healed by vitality healing effects. It does not take void damage, and it is healed by void effects that heal undead.

Speed 40 feet

Melee Hoof +7, Damage 1d8+3 bludgeoning

Gallop

The horse Strides twice, with its Speed increased by 10 feet.

Undead Steed

Undead and creatures allied with them can Command a skeletal steed without needing to attempt a skill check.

Pathfinder Society Scenario #2-11: The Pathfinder TrialsOGL