Melee Mastery skill
Melee Mastery gives you a bonus when using that kind of weapon - This is especially helpful during backtraining. The best way to train the Mastery skills is to train multiple weapons of that type. You can mind lock a Mastery skill using just one weapon, but you're better off training multiple weapons. For clarity thrown weapons count as missile mastery weapons.
Spells and abilities that boost Melee Mastery
Spells and abilities that decrease Melee Mastery