Mounted Combat

A willing creature that is at least one size larger than a rider and that has an appropriate anatomy can serve as a mount, using the following rules.
Mounting and Dismounting

Controlling a Mount

Falling Off
If an effect is about to move your mount against its will while you're on it, you must succeed on a saving throw or fall off, landing with the Prone condition in an unoccupied space within 5 feet of the mount.
While mounted, you must make the same save if you're knocked Prone or the mount is.