Warhammer Expert Feat

Your mastery over a warhammer ensures that your blows never fail to wear down the enemy, becoming an inexorable threat to any foe. You gain the following benefits:

Prerequisite: Proficiency with warhammers

• Ability Score Increase. Increase your Strength or Constitution ability score by 1, to a maximum of 20.
• Battering Blows. When you miss a melee weapon attack with the warhammer, the target takes half the weapon damage the attack would have dealt. This does not count as a hit for things that require you to hit the target (such as spells, Divine Smite, or similar features), but does include modifiers to the attack damage roll.

Source: KCLL, page 188