Source: Unearthed Arcana 85 - Wonders of the Multiverse

Prerequisite: 4th Level, Strike of the Giants (Hill Giant) Feat

You’ve manifested the resilience emblematic of hill giants, granting you the following benefits:

Ability Score Increase. Increase your Constitution score by 1, to a maximum of 20.

Bulwark. When you are subjected to an effect that would move you at least 5 feet or knock you prone, you can use your reaction to steady yourself. You are then neither moved nor knocked prone.