Monster Mount

This spell compels one or more living creatures to serve as mounts for the caster and his companions. The spell affects up to 10 Hit Dice or levels of creatures with Intelligence of 4 or lower. Creatures used as mounts must be of suitable size to carry at least one rider; smaller creatures can be used as pack animals.
Each intended mount receives a saving throw vs. spell. Creatures failing their rolls become docile and obedient, allowing riders to mount them, and moving at the speed and direction indicated by the caster.
To maintain the enchantment, the caster must remain within 10 yards of one of the affected creatures, and each affected creature must remain within 10 yards of another. The affected creatures will do nothing for the caster other than carrying riders and gear; they will not fight (although they will fight to defend themselves), nor will they intentionally endanger themselves. Any overtly hostile act by the caster or a rider against any mount breaks the enchantment for all the mounts.
When the enchantment ends or is broken, the creatures take no action for one round, then behave as their natural instincts direct.

[Tome of Magic]

Sphere: Travelers
(Enchantment/Charm)
Level: 6

Range: 30 yards
Components: V, S
Duration: 1 hour/level
Casting Time: 6
Area of Effect: 20-foot radius circle
Saving Throw: Negates