You slash your arm open and blood gushes from the wound, charged with arcane energy it takes on the properties of acid and expands in the direction you indicate.
You take 3d6 + your Charisma modifier Necrotic damage; this damage cannot be reduced or prevented by resistance or immunity to Necrotic damage. Your blood expands in a 30 ft. cone emanating from you in a direction you chose. Each creature in the area must make a Dexterity saving throw, taking Acid damage equal to the self inflicted damage on a successful save, or twice that on a failed save.
The entire area effected becomes covered in blood and the ground turns into difficult terrain for 1 minute. Each creature standing in the area must make a Dexterity saving throw or fall prone. A creature that enters the area or ends its turn there must also make a Dexterity saving throw or fall prone.
Using a Higher-Level Spell Slot. The damage increases by 2d6 for each spell slot level above 2.
* - (your freshly spilled blood, or a melee weapon with the Light property)