Xerxes target seeking dagger

You enchant the dagger with the anger you have for an enemy of yours. You bind a piece of your enemy to this dagger and then your anger fuels it to find and destroy your enemy. It takes the dagger up to one week to locate and attack the creature. When the dagger finds its target make a melee attack role at advantage against the target. On a hit the target takes 1d4 piercing damage, 8d6 poison damage, 8d8 psychic damage. The target then makes a con save and a wis save as the poison and psychic adversely affects you. If the target fails the con save they become poisoned, and they can't gain the benefits of a long rest. This poison can only be cured by a Greater Restoration. If the target fails the wis save they must then roll on the long term madness table. On a miss the target takes 8d6 psychic damage as the anger from the blade still finds the target. After the blade has found its target it returns to the caste of the spell within one day.