It's completely free for owners of the game. The achievements, like 'Mace in yer face!', are exclusive to Steam users. The DLC is out now to get.
"Fight your way through a multi-level forest encampment and experience conquest mode likes never before in the Forest Hideout or take on new thrills in siege warfare by sending players to the desert to take or defend Jamait Castle," reads the press release.
"If you think you have what it takes to stand out in dual mode, prove it in The Arena; this large coliseum is the perfect place to handle disputes the old fashioned way. The DLC is available for all gamers who have purchased Mount & Blade: Warband."
Who doesn't like achievements especially when there are over 70 of them? Again this is only available to those who own the game through Steam. Do you enjoy Taleworlds' action-RPG Kingdom romp Mount & Blade: Warband? Oh and... horse armour!