Abyssal Slash

You make a wide arching motion with your arms, as your fingertips become imbued with abyssal energies. You tear open a rift into the abyss, leaking its corrupted powers into your current realm. A 15 ft arced mass of abyssal energy appears before you, and flies towards the direction of the target written in the parchment as you cast this spell. The Abyssal Slash is bound to the target and hunts it down until the end of time. Nothing can prevent the Abyssal Slash from reaching its target, save a Wish spell, or if you cast the spell again with a different target.

The arc can traverse indefinitely through dimensions and pass harmlessly through any object magical or mundane (including a magical Wall of Force) that would prevent it from reaching its target. Every time the arc is required to travel dimensional planes or realms, the damage dealt on impact is doubled.

The arc ignores all spell resistances and immunities, as well as armour, walls or other creatures. On impact, the arc deals 1d4 force damage for every mile that it has travelled in order to reach its target.

While the spell is active, you can perform a 10-minute ritual to be made aware of the target's location, regardless of magical protection. At any point in time, you know how far in miles the slash has travelled to reach the target. You are made aware once the arc hits.