Mounted Combatant Feat

You are a dangerous foe to face while mounted. While you are mounted and aren't incapacitated, you gain the following benefits:

Prerequisite: None

• You have advantage on melee attack rolls against any unmounted creature that is smaller than your mount.
• You can force an attack targeted at your mount to target you instead.
• If your mount is subjected to an effect that allows it to make a Dexterity saving throw to take only half damage, it instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.

Source: PHB'14, page 168