Bane's Battle Ballad

Upon casting this spell magic surrounds the user compelling them to turn each hit and strike into a deadlier and more stylish performance and turning each battle cry and grunt into the lyrics of a fine battle poem, the greater the performance the more powerful the spell.
Once the spell is cast choose one of these effects to become activated, when you defeat another foe you may again choose to activate an effect for the duration of this spell.
Failing a concentration saving throw does not cause the spell to end, however, it does de-activate one of the effects (if you have no effects activated the DM may rule that the spell ends, additionally the caster cannot have any other concentration spells active while using this spell)

While this effect is active your AC increases by 1.
While this effect is active you may use your reaction to make a single weapon attack against an opponent that hit you.
While this effect is active your attacks deal an extra 1d6 damage
While this effect is active if an ally is within 5ft of a creature you attack you gain advantage on those attacks.