Slay the Spire - Free Community-made Mod

The card-based RPG Slay the Spire got a free fan expansion called Downfall:

Downfall

Downfall is a full-featured Expansion for Slay the Spire, including a 5th Character, an alternate campaign with SEVEN new characters to play, each with unique cards, relics, potions, and more.

Join the official Downfall Discord community server for all the latest updates, beta builds, and centralized place to post feedback and bugs.

The Hermit - The 5th Hero Character
What expansion would be complete without a new character? The Hermit is a complete, fully fleshed out character, including everything you would expect from a Slay the Spire playable hero. Completely original character & card art, simple but elegant card design, a couple of new mechanics, unlocks, class-specific relics and potions - the full suite.

As the Hermit, the positioning of cards in your hand matters - Dead On cards gain bonus effects while they are in the middle of your hand, so play or exhaust other cards first in order to get them into the center for maximum effect. Embrace the darker side of the Spire and be less afraid of curses, as they can be beneficial to you with the right loadout.

Slay the Slayers - New Downfall Game Mode
Instead of engaging in a Normal Run, you may now play in the alternate Downfall Mode, as one of seven Villain characters (with more to come!), and protect the spire from those who would harm it. Despite there being a large number of them, these Villain characters have just as large of card pools, relics, potions, and everything else you'd expect from a complete character. Villains host slightly more complex designs and fresh mechanics than the Standard run characters, making way for all new strategies in deck drafting and builds.

Downfall Mode is separate game mode from the Standard run, traveling down the Spire's levels instead of up it. Encounter familiar events with theme-appropriate twists, collect and shatter the colored keys to protect the Heart's chamber, and harvest and feed Souls to the Heart to grow in power.

The Slime Boss
Command a squadron of Slime Minions to do your bidding as the dapper Slime Boss! Bash enemies head-first with powerful Tackle cards, which damage yourself as well as your foe. Coat your enemies in horrendous Goop and Consume it for bonus damage and healing, quickly restoring any Tackle damage that went unblocked.

The Guardian
As the Guardian, waylay your enemies with powerful multi-hit attacks as you build up your Strength. Brace yourself, and shrug off the blows to enter Defensive Mode, easily deflecting damage and protecting your health while biting back with Thorns. Using the all-new Gem system exclusive to Guardian, collect Gem cards and socket them into other cards, effectively customizing your cards with bonus effects.

The Hexaghost
Use the right types of cards at the right times to ignite the six fires that surround the Hexaghost for quick additional damage and other bonuses, using the all-new Ghostflame system exclusive to Hexaghost. Incinerate your enemies with Soulburn, and utilize Ethereal cards like never before with Afterlife, a new keyword that causes Ethereal cards to trigger their effects when exhausted.

And Many More...
Discover the other characters Downfall has to offer, each with their own new mechanics, some with even more unique and exclusive systems - and keep an eye out for future updates, because we're not done yet.

“Expansion” content additions to Standard Mode
Like all of the base game characters, the Villains each add a few Relics and Potions to the base game pool.

A new suite of 'Boss' type cards have been added, themed around the Bosses of the Spire. These are generally high-cost, potent cards, and can be purchased at the Merchant, sometimes replacing Colorless cards.

Additionally, a large collection of Events, Curses, Daily Run Modifiers, and Custom run modifiers are also a part of Downfall. The Daily Run system will randomly decide a character among all Heroes and Villains, and randomly choose if the run will be a Downfall run or a Standard run, for maximum chaos.

All Villain characters can be enabled via the Config Menu to be playable in Standard Mode. You will still fight their normal counterparts as bosses.