Cutting Edge

You attach yourself to a willing creature you can see within range with a razor-thin ethereal thread. The thread forms a straight line stretching between you and the target, passing harmlessly through objects and terrain. It extends and shrinks as either of you move, and persists for the duration of the spell. 

When a creature other than you or the target first enters the thread's space on a turn, or starts its turn there, it must make a Dexterity saving throw. On a failed save, the creature takes 3d6 force damage, or half as much on a successful save. A creature can take this damage only once per turn.

While attached, you and the target each know the other's exact position.

The spell ends early if one or more of the following conditions are met:

• either of you is incapacitated,
• either of you teleports,
• the distance between you and the target exceeds the spell's range,
• you and the target are on different planes 

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d6 for every two slot levels above 3rd (4d6 at 5th level, 5d6 at 7th level, 6d6 at 9th level).