Collect the indicated number of crests to unlock the corresponding bonus.

Bonus	How to unlock
Dungbombs in prank boxes around Hogwarts	21 Hogwarts Crests.
Even more health in duels	71 Hogwarts Crests.
Exploding Cauldrons in prank boxes around Hogwarts	48 Hogwarts Crests.
Love Potion in Potions Club	98 Hogwarts Crests.
More health in duels	8 Hogwarts Crests.
More mini-crests with each cast	129 Hogwarts Crests.
Score boost in flying events	38 Hogwarts Crests.
Two Player Dueling Pack 1	Draco and Luna
Two Player Dueling Pack 2	Crabbe and Goyle
Two Player Dueling Pack 2	Training Ground Dueling Arena
Two Player Dueling Pack 4	Paved Courtyard Dueling Arena
Two Player Dueling Pack 4	The Transfiguration Dueling Arena
Two Player Dueling Pack 5	Ginny and Hermione