bs angel has just shared this over on Halo Waypoint -

The Halo 4 Castle Map Pack is the third of three Map Packs from the War Games Map Pass. Currently scheduled for release on April 8th, it will cost $10.00 USD or 800 Microsoft Points and consist of three maps, two new Castle DLC Matchmaking playlists, and 10 new Achievements worth a total of 250 Gamerscore. If you want to learn more about Daybreak, Perdition and Outcast (the maps included in the Castle Map Pack), check out our Castle Map Pack trailer. If you’d like the lowdown on the relevant unlockables that will soon be added to your Gamerscore, take a look at the specifics below!
Halo 4 Majestic Map Pack Achievement
What is Yours is
Also Mine
In Castle DLC Matchmaking, disable a vehicle and then hijack it.
40 points
Dodge This!
In Castle DLC Matchmaking, get two direct Spartan Laser kills in one match.
20 points
Hello Nurse!
In Castle DLC Matchmaking, heal a near-death teammate with Regen Field 5 times.
30 points
That Won't Save You
In Castle DLC Matchmaking, assassinate an enemy who is using a Hardlight Shield.
30 points
Ashes to Ashes
In Castle DLC Matchmaking, disintegrate 6 enemies using Forerunner weapons.
10 points
Beating up the Beat
In Castle DLC Matchmaking, perform 5 melee kills in a single match.
30 points
Sight Seeing
In Castle DLC Matchmaking, complete a match in any mode for each Castle map.
20 points
Scrapyard
In Castle DLC Matchmaking, destroy 2 vehicles during a single game.
30 points
Outta My Way!
In Castle DLC Matchmaking, kill 5 enemies during a match by running them over.
40 points