Risk of Rain 2 doesn't have Steam Workshop support, but it does have mods. And now that the excellent roguelike has hit its 1.0 release, modders are working fast to add new playable characters, skins, and entire new features to the game.
The go-to modding site seems to be Thunderstore.io, where mod updates are rolling in by the hour. With the 1.0 release, Risk of Rain 2's developers added a simple bit of code to check for mods and make it easy for players to play together with the same mods installed (it's also meant to keep mods out of quickplay and the Prismatic Trials, which have a competitive leaderboard.
To get started with modding, you'll want a few APIs used by many mods. If you're downloading anything, it'll likely depend on one or more of these to work:
With those out of the way, here are a few Risk of Rain 2 mods that seem promising so far.
Lemurian - This playable character mod turns you into one of the enemies in Risk of Rain 2, with a full ability set based around its attacks. This mostly involves shooting flames out of your mouth, but there's a cool twist: Stack enough flame hits on enemies and you can power up into the jumbo size Elder Lemurian and use some special skills. This mod has been in the works for a few months and gone through a lot of iteration to fix bugs and work out balance.
Aatrox - Hey, this guy's from League of Legends! One of the most popular mods for RoR2 adds the character to Risk of Rain, complete with some complex, Devil May Cry-inspired melee combo moves. This is the mod to get when you want a more involved character to play.
Sniper - One of the characters from the original Risk of Rain that didn't make the jump to the sequel is the Sniper. And, well, here she is. As you'd expect, the Sniper's abilities are built around taking down enemies from a distance.
ShareSuite - Multiplayer can feel like a competition to get the best items if your group isn't great at sharing, but this mod totally changes the game. When you pick up loot, everyone gets a copy of that item. Money goes into a shared pool, and you can still use recyclers to ditch items without affecting anyone else's inventory. The mod also rebalances the game to take the item sharing into account, but the best part is how configurable it is. For example, you could set it so that everyone gets white-tier items, but rarer reds and boss items are exclusive to whoever picks them up.
StartingItemsGUI - Risk of Rain 2 isn't a roguelike built around the idea of progression; while there are characters and items to unlock, you're still starting every run with the same big fat nothing in your pocket. This mod offers a totally different structure, inspired by other roguelikes like Dead Cells. It introduces money you can use to buy items outside of a run, and you can choose whether those are permanent unlocks or purchases you have to make every time to retain some challenge, but still retain a less random experience than the base game. Or you can just pick whatever items you want and kick ass with your dream build.
SkillsPlusPlus - Another mod that turns RoR2 into a more progression-focused game, though only within a run. With this mod, you earn points that you can use to power up your skills individually.
UrnIgnoresAllies - One boss drops an urn that lets you sap health from anyone around you… which, in multiplayer, means you and your teammates are constantly eating away at each other's health. Fix that annoyance with this mod.
RonaldHuntress - In case you want to make a character look like Ronald McDonald.