The Platinum Dragons Blessing

You have been blessed by Bahamut, The Platinum Dragon.

To receive his blessing is to receive a part of him. Once Per long rest as a Bonus Action you can turn into a platinum dragon for 10 min. This change shifts your draconic resistance to Cold resistance (If your draconic resistance already is cold, then it is changed to immunity). In Addition your Breath Weapon changes into a 30 ft. cone of frost. 

The DC for this saving throw equals your current DC + your proficiency bonus. A creature takes 4d6 cold damage on a failed CON-save, and half as much damage on a successful one. The damage increases to 6d6 at 6th level, 8d6 at 11th level, and 10d6 at 16th level.