How do you unlock new character classes?
The classes in Risk of Rain and how to unlock them are as follows:
Commando: (Unlocked by default.)
Enforcer: (Unlocked by killing the Magma Worm, Wandering Vagrant, and Colossus. Can be unlocked on any difficulty, including Drizzle)
Bandit: (Unlocked by finishing the 3rd stage. Must be done on Rainstorm difficulty or higher)
Huntress: (Unlocked by finding 15 monster logs. Must be done on Rainstorm difficulty or higher. Higher difficulties increase the likelihood to find monster logs)
HAN-D: (Unlocked by opening a crate in the final stage. Can be unlocked in any difficulty, including Drizzle)
Engineer: (Unlocked by repairing 40 drones total. Can be unlocked in any difficulty, including Drizzle)
Miner: (Unlocked by fighting a mini-boss in the Magma Barracks, found on a separate screen entered at the bottom right corner on some map layouts. Can be unlocked in any difficulty, including Drizzle)
Sniper: (Unlocked by beating the game. Can be unlocked in any difficulty, including Drizzle)
Acrid: (Unlocked by fighting a mini-boss in the Underwater Catacombs, found in a cage at the top right corner on some map layouts. Can be unlocked in any difficulty, including Drizzle)
Mercenary: (Unlocked by beating the game 5 times. Can be unlocked in any difficulty, including Drizzle)
You can find more info on the Risk of Rain wiki.
Below you find the difficulty levels at which the characters can be unlocked. These don't all have to be done in one play-through.
Enforcer – Drizzle and up
Bandit – Drizzle and up
Huntress – Rain storm and up (monster logs have a rare chance of dropping from enemies)
Han-D – Drizzle and up, see this video for more information
Engineer – Drizzle and up
Miner – Drizzle and up, Magma barracks has to be on the fourth level see this video for more information
Acrid – Drizzle and up, see this video for more information
Mercenary – Drizzle and up
Loader – Collect 30 or more Different items in Drizzle and up
Chef – collect meat nuggets, bustling fungus, foreign fruit, sprouting egg, and bitter root in one play through drizzle and up.
hope this helped and provided more info. :3