Bronze Dragon's Wrath

A javelin of wrath appears in your hands. It has all the properties of a normal javelin, but instead deals 2d8 lightning damage on a hit, and comes back to your hand after every throw. In addition, if you hit a target twice with this javelin in a turn, it becomes polarised. While polarised this way the next 2 attack rolls made with metallic weapons, or dealing lightning damage, against the target have advantage, thanks to the attraction of the electricity.
At Higher Levels. When you cast this spell using a 3rdor 4th-level spell slot, the damage increases to 3d8. When you cast it using a 5th- or 6th-level spell slot, the damage increases to 4d8. When you cast it using a spell slot of 7th level or higher, the damage increases to 5d8