Undead Entanglement

If a creature within 30 ft of you dies, you may use your reaction to cast Undead Entanglement on it. You may also cast this using your bonus action on a target that has already been dead for some time (determined by DM).

Vines pierce the body of the dead creature in such a way to prevent it from resurrection, and giving the vines control of the body. Until dispelled, you may command the plants to do whatever you wish. The body has hit points equal to half its total hit point total while it was living. It's AC is the base creature’s AC-2.

The body will not hold any swords, shields, or otherwise. It will fail all saving throws and takes double damage from fire. You can command the body to attack. If the attack is successful, the target takes 1d8 + the creature’s strength modifier in bludgeoning damage. 

Due to the grotesque nature of the body and plants, it also provokes any other enemies in the vicinity. Any enemies within eyesight of the creature must make a Charisma saving throw. On a failure, the creature must focus on the Entangled being until it has been destroyed. If the enemy witnesses the creation of this monster, it makes this save at disadvantage.

You can use your bonus actions to command the body to do whatever you please on your turn. It will continue to do its previously issued command until told otherwise. At the time of summoning, you may give the body an order at no penalty to your bonus action or regular action. If you fall unconscious, become incapacitated, or die, the body will continue to carry out its last given command until it's task is completed, or it is destroyed. If the creature's last order was to attack the closest target, it will continue to attack the closest target, regardless if the target is a friend or enemy to you. 

Additionally, if the creature crits on it's attack roll, the creature deals 2d8 + the creature’s strength modifier of bludgeoning damage, and the target must make a strength save or fall prone if it is the same size or smaller than the Entangled creature. If the target creature had succeeded it’s Charisma saving throw, it must also make this roll again. At 6th, 12th, and 18th Druid level, this spell can entangle an additional creature per tier (2 at 6th, 3 at 12th, 4 at 18th).