if not using Sangromancy this spell is a Evocation school
Casting Time: Action , Range: 300 Feet , Components: V (Vocal) - S (Somatic) - M (Material) , Duration: Up to 1 Minuet (Concentration)
Special Material: a Ruby worth at least 100 gp
Effect
As part of casting this spell you must expend six hit dice or the spell automatically fails.
When you do, blood flows from your body then crystallizes into a barbed arrow, which launches at a creature of your choice within range. Make a ranged spell attack against the chosen creature. On a hit, roll the hit dice expended to cast this spell, and the creature takes piercing damage equal to the result.
Once lodged in the creature, the bloody arrow begins to burrow toward its heart, rendering it vulnerable to further attacks. At the start of the creature’s next turn, it must make a Constitution saving throw. On a failure, attacks against the creature score critical hits on a 19 or 20 on the attack roll.
At the start of each of the creature’s turns after that, it must repeat the Constitution saving throw or the critical hit range on attacks against the creature increases by 1 again. If the creature succeeds on three of these saving throws (these successes do not need to be consecutive) this spell ends. The increased critical hit range ends when the spell does.
At Higher Levels
Lore, some nice lore flavour and/or history