Erethan's Ray of Enfeeblement

A greenish-black beam of enervating energy springs from your finger toward a creature within range, remaining there as a link between the target and your hand, and giving the target a dark-green aura. The target makes a Constitution saving throw against the spell. On a fail, it deals only half damage with weapon attacks, has Disadvantage on all Strenght and Dexterity saving throws and Disadvantage on all Strenght and Dexterity ability checks until the spell ends.

The spell ends after a minute, if you use your action to do anything else, if you break Concentration, if the target moves outside the range of the spell or moves behind total cover, or if it succeeds a Constitution saving throw against the spell,  which it can make at the end of each of its turns.