If Your Mount Falls in Battle: If your mount falls, you have to succeed on a DC 15 Ride check to make a soft fall and take no damage. If the check fails, you take 1d6 points of damage.
...so if I fall off my Pegasus and make my ride check, I take no falling damage?
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:P
falls as in dies... so falling from your horse to the ground
and then you would add the damage from how high you were in the air