Silver Dragonmark

You have manifested a  silver dragonmark. You gain the following benefits:

You can innately cast the ray of frost cantrip at will. In addition, you may cast ice knife innately through your mark. Once you cast it, you must finish a short or long rest before you can cast it again through the mark. Constitution is your spellcasting ability for these spells. 

When you cast ice knife through your mark, you can expend one of your Hit Dice and roll it. If you roll an even number, you gain a number of temporary hit points equal to the number rolled. If you roll an odd number, one random creature within 30 ft. of you takes force damage equal to the number rolled. If no other creatures are in range, you take the damage.