Formula: Enchant Weapon - Minor Beastslayer

Formula: Enchant Weapon - Minor Beastslayer teaches an enchanter to enchant beastslaying.

Source
It is a world drop from mobs as low as level 11 and as high as level 26, though it is most common between level 15 and 20.

Enchant
The enchant permanently enchant a melee weapon to do 2 additional points of damage to beasts. Despite the low attack power upgrade, this enchant remains popular because it is the cheapest enchant that provides a weapon glow.