SpeedFog

Elden Ring mod that generates short randomized runs (~1 hour) with balanced parallel paths. Supports base game and Shadow of the Erdtree DLC.

Unlike FogRando which randomizes the entire world, SpeedFog creates a focused path from Chapel of Anticipation to a random major boss with no dead ends.

Features

Run structure

• Short runs: ~1 hour target duration (configurable)
• Balanced paths, no dead ends: parallel routes have similar length/difficulty, and every path leads to the final boss
• Run modes: restrict cluster types for a boss rush, legacy-dungeon marathon, dungeon crawl, and more (allowed_types)
• Configurable final boss: Radagon, Promised Consort Radahn, or any major boss (weighted candidates)
• Zone control: force specific zones/bosses to appear, or exclude them entirely
• Difficulty curve: configurable start/end tiers with linear or power progression
• Seed-based: share seeds for identical runs

Gameplay

• Item randomization: optional Item Randomizer integration (auto-upgrade, placement presets, reduced upgrade costs, all crafting recipes)
• Boss randomization: optionally swap boss entities across arenas (minor-only or all), with arena-size constraints and "boss-only" run support
• Care package: optional randomized starting build (weapons, armor, spells, talismans)
• Starting loadout: key items, Great Runes, whetblades, talisman pouches, and consumables given at start (no softlocks)
• Rebirth: respec stats at any Site of Grace (consumes a Larval Tear; a stack is given at start)

Quality of life & cosmetics

• QoL tweaks: Chapel Site of Grace, faster grace animations, menu input delay removed (by the item randomizer's RandomizerCrashFix.dll, when item randomization is enabled), etc.
• Cosmetic themes: customizable victory banner and opt-in summer theme
• Racing support: zone-tracking flags, death markers, and phantom-skin rewards for competitive play

Packaging

• Self-contained output: includes ModEngine 2 and a launcher

Requirements

• Elden Ring (Steam version)
• Python 3.11+
• .NET 10.0 SDK
• Wine (Linux only)

Installation

1. Download Dependencies

From Nexusmods (requires account):

• Required: Elden Ring Fog Gate Randomizer
• Optional: Elden Ring Item and Enemy Randomizer - for item/enemy randomization

2. Clone and Setup

git clone https://github.com/rbignon/speedfog.git
cd speedfog

# Install Python dependencies
uv pip install -e .

# Install sfextract (extracts DLLs from FogRando)
dotnet tool install -g sfextract

# Extract dependencies, generate derived data, build C# writers, and install ModEngine 2
python tools/bootstrap.py \
  --game-dir /path/to/ELDEN_RING/Game \
  --fogrando /path/to/FogRando.zip \
  --itemrando /path/to/ItemRandomizer.zip

# Or FogRando only (no item randomization)
python tools/bootstrap.py \
  --game-dir /path/to/ELDEN_RING/Game \
  --fogrando /path/to/FogRando.zip

3. Configure

cp config.example.toml config.toml
# Edit config.toml to set your game directory and preferences

Usage

Generate and Build a Run

uv run speedfog config.toml --logs

Output is self-contained in seeds/<seed>/:

• graph.json - DAG definition
• logs/spoiler.txt - Spoiler log
• logs/generation.log - Structured generation log
• modengine2/ - ModEngine 2 binaries + config_speedfog.toml
• lib/ - runtime DLLs loaded by ModEngine 2 (item randomizer DLLs, when enabled)
• mods/ - Generated mod files
• launch_speedfog.bat - Windows launcher

CLI Options

uv run speedfog [config_file] [options]
  --output/-o DIR         # Output directory (overrides config)
  --logs                  # Generate spoiler log and generation log
  --seed INT              # Random seed (overrides config, 0=auto-reroll)
  --max-attempts INT      # Max retries for auto-reroll (default: 100)
  --verbose/-v            # Verbose output
  --no-build              # Skip mod building (graph.json only)
  --game-dir PATH         # Game directory (overrides config)

Generate Only (no mod build)

uv run speedfog config.toml --no-build --logs

This creates only graph.json and logs/. To build manually, see writer/README.md.

Play

The output folder is self-contained with ModEngine 2 copied from data/packaging/:

./seeds/<seed>/launch_speedfog.bat

Playing on a frozen copy of the game

By default ModEngine 2 launches the Steam install. To keep playing SpeedFog on an older game version while Steam updates the main install, copy the whole ELDEN RING/Game folder somewhere else before the update, then point the launcher at it, either with an environment variable:

SPEEDFOG_GAME_PATH=D:\Games\ELDEN RING 1.16\Game

or with a per-machine config file at %APPDATA%\SpeedFog\config.ini:

game_path=D:\Games\ELDEN RING 1.16\Game

The value may be the Game folder or the eldenring.exe inside it; keep the copy on a path without accented or non-Latin characters. Both settings live outside the seed folder, so they apply to every seed. A seed distributor may also ship the same game_path= line in a config.ini at the seed root, next to launch_speedfog.bat (SpeedFog Racing writes it from the player's account settings); it is only used when neither the environment variable nor the per-machine file is set, so a local setting always wins. None of these is the per-seed backups\config.ini, which only holds backup settings. The launcher prints which game it uses and refuses to start if the configured path does not exist. Steam must still be running. The save file (%APPDATA%\EldenRing\<id>\ER0000.sl2) is shared by both copies: do not open the updated game with a save you still need on the older version, and keep the backup daemon enabled (see docs/save-backup.md).

Configuration

Edit config.toml (see config.example.toml for all options).

How It Works

SpeedFog builds a DAG (Directed Acyclic Graph) of zones with an exit-driven algorithm.

Layer by layer, it picks a set of clusters of the same type and routes the previous layer's fog-gate exits into them, reusing spare exits to widen the graph toward max_parallel_paths and to weave cross-links between the parallel branches, until a convergence phase narrows the width back down to a single node before the final boss.

        Chapel of Anticipation
                 │
            ┌────┴────┐        ← Chapel and Roundtable fogs
            ▼         ▼
         Legacy     Legacy     ← saturation: use most exits to open
         Dungeon    Dungeon      parallel branches (up to max_parallel_paths)
            │  \   /  │          and cross-link them
            │   \ /   │
            ▼  /   \  ▼
          Boss       Boss      ← reuse entrance as exits on boss arenas
            │  \   /  │          to prevent dead ends
            │   \ /   │
            ▼  /   \  ▼
          Cave     Catacombs
            │         │
            └────┬────┘        ← convergence: funnel the branches back
                 ▼               down to a single node
            Final Boss         ← final boss (final tier)

• Exit-driven routing: each layer's clusters are fed by the previous layer's fog-gate exits; splits, merges, and cross-links all emerge from this routing rather than being scheduled
• Fog-gate reuse: arena's entrance fogs double as exits toward the next layer, so the same gates that let you in can carry you onward (bidirectional gates)
• Balanced branches: cluster weights (≈ traversal time) are weight-matched within each layer, so parallel routes stay comparable and races stay fair
• Enemy scaling: each layer carries a tier from start_tier to final_tier (linear or power curve), applied through FogRando's per-zone scaling
• Key items at start: progression items are granted up front to prevent softlocks

Contributing

See CONTRIBUTING.md for development setup and guidelines.

Credits

• FogRando by thefifthmatt - Core fog gate system
• Item Randomizer by thefifthmatt - Item/enemy randomization
• SoulsFormats - File format library
• ModEngine 2 - Mod loading

License

SpeedFog is licensed under the GNU General Public License v3.0 or later (GPL-3.0-or-later). See LICENSE for the full text.

Copyright (C) 2026 Romain Bignon

SpeedFog adapts logic from FogRando (credited above) and links against third-party binaries (FogMod, RandomizerCommon, SoulsFormats, ModEngine 2) that users download at setup time. Those binaries are not redistributed in this repository and remain under their respective licenses.