Progression

As you beat Missions you will acquire Experience to level up your heroes. You will also be receiving chests which can be opened to obtain Equipment. By equipping new items you can raise your Hero Power and unlock increased difficulties.

Leveling Heroes
Players gain experience for the character they played at the end of a run. The amount of XP gained depends on the difficulty, how much of the map was completed, number of players alive, and the number of tomes/grims collected.

Careers
At level 1, only one career is available. The second is available at level 7, and the third is available at level 12.

Skills
Skill points are awarded at levels 5,10,15,20,25. Up to one skill can be chosen at each available tier.

Rooms
At level 10, the a character's bunk in the keep is replaced by a room.

Crafting
A character periodically gains the ability to craft specific weapons after leveling up.

Difficulties
Difficulties are unlocked based on the hero power of a character.

Achievements
You can view a list of Achievements here.