Beats of a bleeding heart*

As a reaction, you release a drop of your own blood onto the ground and the symbol of your chosen deity appears at your feet on the ground and marks your target on the chest right where their heart should be, locking eyes with the target your hearts syncopate, the target's heartbeat increases in speed and volume until they suffer the damage of their own hearts dark intent.

allowing their spell to reach you, you may attempt a constitution save (Dc = PC spellsave dc) to channel their malice through the symbols and send it back to them increasing the damage dice by one of the appropriate corresponding dmg dice.

Failure of constitution save results in both characters suffering half total dmg then Target takes 1 additional corresponding dmg dice.

The dmg type becomes necrotic or radiant.

 if the caster is fiend, undead or celestial increase the damage further by one corresponding damage dice .

At higher levels: when expending a spell slot above 3rd level to cast the spell the dmg reflected is increased by one appropriate damage dice against the original caster