Bloodvenom Blade
Weapon (dagger), very rare (requires attunement)
This dreadful blade rewards cunning savagery and vicious bloodshed by granting its wielder the cruelest power of death. Every strike against your foes fuels the weapon with a deadly toxin, siphoned from the very essence of your enemies, and when it has been quenched it can unleash a lethally potent strike. When you hit a living creature that has blood with this weapon and deal damage, the weapon gains a charge up to a maximum of 6 charges. When you hit a creature with the bloodvenom blade while it has maximum charges, you may expend all its charges (no action required) and cause the blade to deal an additional 8d10 necrotic damage to the target. For every hour that passes since the blade last gained a charge, it loses 1 charge until it is empty.