Aberrant Dragonmark

At the DM's option, a character who has the Aberrant Dragonmark feat has a chance of manifesting greater power. Upon reaching 10th level, such a character has a 10 percent chance of gaining an epic boon from among the options in chapter 7 of the Dungeon Master's Guide. If the character fails to gain a boon, they have a 10 percent chance the next time they gain a level. If the character gains a boon, the DM chooses it or determines it randomly. The character also permanently loses one of their Hit Dice, and their hit point maximum is reduced by an amount equal to a roll of that die plus their Constitution modifier (minimum reduction of 1). This reduction can't be reversed by any means.

You have manifested an aberrant dragonmark.

• Increase your Constitution score by 1, to a maximum of 20.
• You learn a cantrip of your choice from the sorcerer spell list. In addition, choose a 1st-level spell from the sorcerer spell list. You learn that spell and can cast it 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 the 1st-level spell 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 feet of you (not including you) takes force damage equal to the number rolled. If no other creatures are in range, you take the damage.

You have manifested an aberrant dragonmark. Determine the appearance of the mark and the flaw associated with it.