Use the Deluminator

Complete "Horcrux and the Hand"

Complete "Love Hurts"

Complete "Just Desserts"

Complete Year 5

Defeat Bellatrix as any Sirius Black character variant in a duel

Complete "Kreacher Discomforts"

Complete "Dumbledore's Army"

Turn the sound down to 0 and music off in the options menu whilst in the library

Scare 20 students using a ghost character

Defeat Harry (as Voldemort), in the Graveyard

Defeat 20 spiders with Ron

Destroy 50 Devil's Snare plants