Using mana to infuse a martial weapon of your choice, roll a hit die from your pool. You reduce your hit point maximum by the result you rolled and for the next X attacks where X is your proficiency bonus, you deal the result rolled as additional damage either as fire or necrotic (your choice). Your weapon stays infused until all X attacks are successful. In the event of a critical hit, the damage from this infusion is NOT doubled as the roll has already charged it. You may only infuse a weapon once per short or long rest.