Arkane revealed a number of new information regarding Redfallits first-person shooter in a recent Q&A, including the difficulty in solo and co-op play as well as the secrets to unlocking cosmetic items.
Arkane has confirmed that, with the exception of pre-order bonuses, all cosmetics may be obtained simply by exploring the game and as a reward for fulfilling missions. Players will probably be surprised to know that this type of content isn't locked in season passes or the like.
The game will be more difficult if you play solo, according to the developers of Redfall. In co-op, Arkane said he "considers campaign progress and difficulty, but also the number of players."
The kinds of enemies you encounter depending on the size of your group will vary, as will solo play abilities, and the frequency of elite traits. These are not generalized changes. Some encounters will always be easier or harder than others, and some may not change at all. But that's not the purpose: things should always be more challenging if there are more players.
We know that Redfall will have "thousands of lines of text" that will go into the legend.