Actually bought this game twice... once as a bargain bin special, then bought the full pack on Steam
MB is a medieval simulation here you play a guy (or girl) out to make his or her fortune and fame as adventurer / mercenary. The most interesting part is third-person real-time combat, where you need to block / parry / attack using a variety of weapons, including two-handed weapons, one-handed weapon, one-handed weapon with shield, bows and arrows, crossbows, throwing weapons (knives, rocks, javalins, etc.) and you will do fighting on foot AND horseback (yes, shoot arrows too).
You roam this world with multiple factions, and war parties passing back and forth, bandits roam the countryside, and you need to raise a band, and later, an army, swear allegiance to a particular lord (and raid his enemies), keep your band fed, trade for supplies and equipment (and food), and when it is time, besiege enemy castles and storm them (or defend your lord's castles against invaders).
Later expansions added larger parties, better tactical controls, as well as firearms and formations.
It's a pretty weird game, as it's partly like Sid Meier's pirates (lots of random encounters, and freedom to do almost anything), but with more randomness and 3D graphics.
I will report back with progress of my campaign.