Difficulty

There are four difficulty levels in the base game (Recruit, Veteran, Champion, Legend), with the addition of Cataclysm in the Winds of Magic expansion.

General
Each difficulty level has a Power level requirement; in order to start a mission with a party, each party member will have to fulfill these level requirements. Note that players joining the game through invites or through connecting with a friend after a game has started do not have to have these requirements fulfilled.

Mission difficulty influences a number of game mechanics, including enemy stats and friendly fire. Many of these changes are not listed in the available flavor text, but are listed here. The flavour text also talks about enemy becoming more "aggressive", but this does not mean the aggro range of enemies increases. It might point towards the enemies having more mass and resistance to stagger, which makes them harder to keep at bay.

Recruit
Starter difficulty, enemies have normal behavior. Pickups are common. Additionally, each player starts with a Healing Draught.

Veteran
Enemies are resistant to hits, have high health, are aggressive and hit hard. Pickups are uncommon.

Champion
Enemies are very resistant to hits, have very high health, are very aggressive and they hit very hard. Pickups are scarce. Ranged weapon Friendly Fire.

Legend
Enemies are ridiculously resistant to hits, have a ridiculous amount of health, are ridiculously aggressive and hit ridiculously hard. Pickups are ridiculously rare. Ranged weapon Friendly Fire.

Cataclysm
The End Times are upon us. You will not survive. Ranged weapon friendly fire. Only for heroes with the absolute highest level of skill.