DND 5th Edition

Source: Unearthed Arcana 83 - Giant Options

Prerequisite: 4th Level
You’ve manifested the icy might emblematic of frost giants, granting you the following benefits:

Born of Ice. You have resistance to cold damage.
Frigid Vengeance. When a creature hits you with an attack roll, you can use your reaction to retaliate with a burst of magical ire. The creature must succeed on a Wisdom saving throw (DC equals 8 + your proficiency bonus + your Constitution modifier) or be frightened of you until the start of its next turn. You can use your reaction in this way a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.