Sunsword (weakened)

Longsword +1, finesse
Deal radiant damage. When you hit an undead
with it, extra 1d4 radiant damage.
The blade emits light in 10 feet + 10 feet. The
light is sunlight. As an action expand or reduce
its radius by 5 feet each.
(max 20 feet each, min 5 feet each)