Umbral Agony

You hurl an orb of dreadful umbral energy at a creature within range. Make a ranged spell attack against the target and feel your soul wither ever so slightly. On a hit, the target takes 1d10 Necrotic damage, additionally the target's speed is reduced by 10 feet until the start of your next turn

Cantrip Upgrade. The damage increases by 1d10 when you reach levels 5 (2d10), 11 (3d10), and 17 (4d10).