Harry Potter and the Deathly Hallows Part 2: Collectibles The Lost Diadem

The starting area, just take a look around. The area isn't big.

Prize (music):

Wandering Part 7 - Surrender

He collectible can be easily found where one of Draco's friends will attack you from the bunker for the first time.

Prize (character):

Gregory Goyle

During the next attack, go round the enemy barricade from the left side.

Prize (character):

Draco Malfoy

The fourth collectible can be found nearby the third one. Go through the door opened by Hermione and head to the cache on the right.

Prize (challenge):

A Giant Problem

After destroying the third bunker, take a walk around the location. You will find the orb between the junk.

Prize (challenge):

The Lost Diadem

A collectible that pretty much collects itself on your way to the final fight with Draco.

Prize (character):

Blaise Zabini