Runespark Shield

Spell Lists: Wizard, Sorcerer, Artificer
Abjuration cantrip
Casting Time: 1 action
Range: Self
Components: V, S, M (a garnet with an abjuration rune carved into it, worth at least 15 gp)
Duration: 1 minute

Invoking the rune magics of old, you create a field of arcane lightning around yourself which lasts for the duration. The color of the lightning matches the color of the garnet used in the spell's casting. The next time a creature hits you with a melee weapon attack during the spell's duration, that creature must make a Constitution saving throw. On a failed save, the creature takes 1d6 lightning damage and has disadvantage on any further weapon attacks it makes until the end of that turn. If the save fails by 5 of more, the creature is instead Stunned until the end of that turn. A creature resistant or immune to lightning damage suffers none of the spell's additional effects.

The spell's damage increases by 1d6 when you reach 5th level (2d6), 11th level (3d6), and 17th level (4d6).