Microsoft and 343 Industries have christened this "Halo Week: Drop Shock," bringing a steady stream of new content and special deals for Halo 4. It all started with the Castle Map Pack that launched yesterday, but the companies have special challenges and discounts in store too.

Today, 343 is debuting the second volume of the Halo 4 original soundtrack. Tomorrow, the game will add 14 daily and six weekly Extra XP challenges, ranging across various modes from Campaign to Spartan Ops and War Games. Each were designed to drop more XP than standard challenges. On Thursday, playing and completing any five Spartan Ops missions will enter you in a drawing for a t-shirt. All Spartan Ops episodes are unlocked for matchmaking this week too. Finally, on Friday, the previous packs will go on sale: the Map Pass for $20 (reduced from $25), and the Crimson and Majestic packs down to $7.50 from $10.