Special Properties:

You gain a +1 bonus to attack and damage rolls made with this weapon.
For every times you make an attack roll using this weapon against a target (regardless of whether the attack hits or misses), the weapon gains a cumulative -1 penalty to attack rolls and cumulative -1 penalty to damage rolls.
If the total penalty reaches -6, the weapon is destroyed.
This penalty can be removed by casting the Mending spell on the weapon.

Proficiency with a Longsword allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Bonus: Magic, If the total penalty reaches -6, the weapon is destroyed., Damage, Combat, Versatile, Sap