These reins allow your mount to briefly break the bonds of gravity.  Reins of the Sky Lancer have 4 charges, which are renewed each day at dawn.  Spending 1 or more charges grants your mount a benefit as described below.

1 charge: +10 competence bonus on Jump checks for 10 rounds.

2 charges: Fly at normal land speed (average maneuverability) for 5 rounds.

3 charges: Fly at double normal land speed (perfect maneuverability) for a round.

In addition, the reins provide the owner with the Mounted Combat feat, whether or not he meets the prerequisites.

These sturdy leather reins were first used by a famous warrior who fought from griffonback.  They remain wrapped around the owner's wrists, until the owner is mounted, at which point they unwrap and attach themselves to the mount's bit.