Ethereal Essence

You call upon the energy of the ethereal plane, and channel it to a creature you can see within range. The target rolls a CON save of  DC8 + Proficiency bonus +Spell Casting Modifier. On a failed save, the target takes 2d8 necrotic damage and it's speed is slowed by half until the end of it's next turn. On a success the target only takes half damage and does not suffer from the slowed effect. For every spell level cast above first level, add an extra d8 to the roll.