Vavance's Jellylegs jinx

You weaken the wings, fins or legs to make walking quite difficult. You target a creature that you can see within range, The target must make a constitution saving throw, on a fail they take 2d8 acid damage and have their movement speed reduced to 5 feet. If the target has multiple movement speeds the caster choose the movement type affected. If they succeed they take half damage and aren't slowed. A target can repeat the saving throw and the end of each of their turns to end the effect on themselves