Cosmic Breach

Something fell from the sky last night. It is still humming, and it wants to go home.

Free to play, include in modpacks (link to this page, don't re-upload), and make videos and streams, monetized ones included.

Cosmic Breach is an action-RPG dimension mod for NeoForge 1.21.1. On your first night a star falls near you. Build a ring of copper around it, step into the hole it opens, and fall up into Aetheria: a shattered sky realm stacked in four levels, four bosses. The combat is rebuilt for it: committed attacks, dashes with invulnerability, parries, and telegraphs you can read.

The first two levels are described below. The rest stays a surprise.

Getting there (about 20 minutes into a new world)

• The Starfall. At your first sunset a Starfall Shard streaks across the sky and lands nearby under a beam of light. Break it by hand and you get the Starfall Codex, the in-game guide, open at "Build a ring".
• The Breach Ring. Eight frames of copper and stone, laid flat in a ring. Use the shard on it and the ground opens onto a sky. Step in and fall up.
• Fallen Rifts. Small meteor craters in the Overworld hold a half-buried ring and a chest.

No iron, no diamonds, no rare drops: any seed gets you there.

Level 1: the Upper Reach

Floating islands in full daylight under a ringed gas giant. Shattered Spires, Sunfield Terraces, and herds of Lumen Stags that you can tame, saddle and ride. Shardlings, crystal pack hunters, are meant to be hard with a vanilla sword.

Boss: the Prism Colossus. A crystal giant fused into the pillar at the top of the Crown Spire. Parry its Prism Slam, dash through its Facet Sweep, and turn the crown crystals to bounce its own laser back into its core. At zero health it shatters into three shards that you have to kill fast.

Level 2: the Drift

Asteroid belts drifting under a starry sky, with open lanes between them. Tame a Drift Manta, a stingray the size of a boat that flies, and ride it across the gaps. Level 2 feeds you as well: Manta Fillets, Starhide, Rimeglass and Nebulite.

Boss: the Thalassine Leviathan. A sky whale as long as a river, circling inside its Rift. Its song tells you what it will do next: breach dives, a pulling song, and a moment when it moors itself and you can strike. If you fall below its arena, the air under it catches you and lifts you back up.

The Astral Forge

One crafting station that tiers up as you progress. Forge Meridian, a starsteel blade with its own moveset, and armour sets with set abilities. The forge screen has tabs for weapons, armour, tools, mount gear and other, and full tooltips on everything. The forge accepts level materials in place of overworld ones, so you never have to go back to the Overworld for food, leather, string or tools.

Combat and systems

• Dash (Left Alt) with invulnerability frames. Parry (V) anything that glints gold.
• Resonance fills as you fight and powers your weapon. The world is the meter: your blade and armour glow instead of the HUD filling with bars.
• Attunement (K): level up, spend stat points, unlock tiers.
• Set abilities (Z) on armour sets.
• Mounts: the Stable Crystal stows a tamed mount with everything on it and sets it down again where you want it.
• Every boss speaks, with on-screen captions. They react to how you fight.
• A shrine at every boss. Right-click one to save your place. While a shrine is your respawn, dying in the mod's levels keeps your inventory and experience.

All keys can be changed under Options, Controls, Key Binds, "Cosmic Breach".

Multiplayer

Built for co-op and tested on a dedicated server. Loot, XP and attunement are per player, so nobody fights over drops, and boss health scales with the number of players.

Servers: set allow-flight=true in server.properties. The mod's movement (dashes, mounts, the fall up through the ring) can look like flying to vanilla's anti-fly check, and without the setting players get kicked. Everyone on a server, and the server, needs the same 1.1.x version. 1.0.x clients cannot join a 1.1 server.

Requirements

Required mods (the CurseForge app installs them for you):

• GeckoLib
• Curios API
• GuideME
• playerAnimator

NeoForge 21.1.252 or newer on Minecraft 1.21.1, Java 21. Needed on both client and server.

Known to work with Sodium, and Better Combat with Combat Roll. A shader pack changes how some places look, so play with shaders off for the intended look.

Practice arena: with cheats on, /cosmicbreach sandbox builds an arena in the sky above you and sends waves at you. It moves your spawn and turns on keepInventory, so try it in a spare world.

How it was made

Cosmic Breach was built by Claude Opus 5.5 in Claude Code: the design document, the code, the textures, the models and animations, the boss AI, and a hidden test client that played the mod and checked its own screenshots. Nate gave it the idea and played the result with a friend.

Textures, models and most of the sound and music are generated by code in the repository. Voice lines were made with ElevenLabs v4, and some sound effects with ElevenLabs (elevenlabs.io), under a paid plan with a commercial licence. Voices by ElevenLabs. Full credits are in CREDITS.md, inside the jar and in the source repository.

Licence and permissions

• Free to play, include in modpacks (link to this page, don't re-upload), and make videos and streams, monetized ones included.
• Code: MIT.
• Assets (textures, models, animations, sounds, music, text): All Rights Reserved. Please don't re-upload them, redistribute them outside modpacks, or sell them.
• Excluded from the MIT grant: the ElevenLabs audio (credited, covered by ElevenLabs' terms) and one modified Minecraft shader file, which stays under Mojang's terms.

Full text: https://github.com/CalmDownNova/cosmic-breach/blob/main/LICENSE

Minecraft is a trademark of Mojang Studios. This is not an official Minecraft product and is not approved by or associated with Mojang or Microsoft.

Spoilers

Nate has played the first two levels so far. If you get further, please keep the lower levels out of comments and issue titles.

Links

• Source: https://github.com/CalmDownNova/cosmic-breach
• Issues: https://github.com/CalmDownNova/cosmic-breach/issues