Blackened Tendril

You prick your finger and summon from within you the black of the Abyss. Your veins go black as a deep black tendril springs from your hand to a creature you can see within range. Roll a melee spell attack. On a hit, the target takes 1d6 piercing damage as the tendril burrows into it's skin. If the spell hits a target, the target must make a DC 15 Strength Saving Throw or be held in place as the tendril travels through and embeds itself into the ground, reducing the targets movement speed to 0. While it is restrained in this way, the target takes 2d6 necrotic damage at the start of each turn as the necrotic force spills into the target's wound. It can repeat the strength save at the end of each turn to escape the tendril's grasp/