Tendon Whip

You wrap the tendon around your wrist like a bracelet and it extends out to a whip's length, which lasts for the duration. It counts as a martial melee weapon with which you are proficient, even if you do not have proficiency with martial weapons. It deals 1d4 slashing damage and 2d4 necrotic damage on a hit and has the finesse and the finesse. In addition, when you use the whip against the undead, the necrotic damage is considered radiant damage.

If you drop the whip or are disarmed, it dissipates at the end of the turn. Thereafter, while the spell persists, you can use a bonus action to cause the whip to reappear in your hand.

If an enemy attempts to leave the 15-foot space around you while the whip is in your hand, you may use your reaction to make an attack roll as an opportunity attack. On a hit, the creature must make a Strength Check against your Spell Save DC or be grappled. On a success, the tendon snaps with a loud crack that can be heard from 100 feet away and the spell ends.

The enemy can attempt to break out of the grapple with a Stength Saving Throw every turn after this check.

At Higher Levels. When you cast this spell using a 3rd- or 4th-level spell slot, the necrotic damage increases to 3d4. When you cast it using a 5th- or 6th-level spell slot, the damage increases to 5d4. When you cast it using a spell slot of 7th level or higher, the damage increases to 6d4.