Seasonal SLS Bridge

Seasonal SLS Bridge connects Seasonality with StarLevelSystem to give Valheim's creatures seasonal traits shaped by the world around them.

The goal is simple: make the world feel more alive and less predictable without changing StarLevelSystem itself, creature levels, spawn rates or loot.

Features

When a new creature appears, the mod checks the current Seasonality season and gives it a chance to receive a seasonal StarLevelSystem modifier.

In 1.3.0, the season is no longer the only influence. The creature's birth biome and natural affinity can also affect which seasonal traits fit it best.

This means winter does not feel exactly the same in the Mountains as it does in the Ashlands, and a creature naturally associated with fire, cold or poison can react differently to the same season.

Winter --- Vetrbarn

Winter strongly favors cold-oriented creatures.

Possible modifiers include:

• Frost
• ResistFrost
• Big
• StaminaDrain
• ResistPierce
• ResistSlash
• ResistBlunt
• EitrDrain

Frost has a 95% primary chance before ecological adjustments.

Cold environments and naturally cold creatures can reinforce winter's influence, while strongly fire-oriented environments or creatures can resist it.

Spring --- Várbarn

Spring favors poison, adaptation and strange elemental mutations.

Possible modifiers include:

• Poison
• ElementalChaos
• PoisonNova
• ResistPoison
• Fast
• Evolving
• Splitter

The main seasonal chances are:

• Poison --- 65%
• ElementalChaos --- 25%

Poison is now ecologically limited in early-game environments. It is much less common where it would be especially punishing or unnatural, while poisonous creatures and appropriate biomes can still strongly favor it.

ElementalChaos remains possible in early biomes and is not restricted by this Poison protection.

Summer --- Sumarbarn

Summer favors heat, fire and aggressive elemental effects.

Possible modifiers include:

• Fire
• FireNova
• ResistFire
• Lightning
• Fast
• Brutal
• Big

The main seasonal chances are:

• Fire --- 70%
• Lightning --- 15%

Warm environments and fire-oriented creatures can strengthen summer's influence, while cold environments can reduce it.

Autumn --- Haustbarn

Autumn is the most unstable season, favoring lightning, poison and spiritual effects.

Possible modifiers include:

• Lightning
• Poison
• ElementalChaos
• SoulEater
• ResistSpirit
• Alert
• ResistPoison
• Big

The main seasonal chances are:

• Lightning --- 40%
• Poison --- 30%
• ElementalChaos --- 20%

Autumn remains intentionally varied, with local ecology helping determine how its instability appears.

Other listed modifiers act as secondary possibilities when the main seasonal modifier is not selected.

Ecological Affinity

Seasonal SLS Bridge 1.3.0 introduces an ecological affinity system.

Seasonal selection can now consider:

• the current season;
• the biome where the creature was born;
• the creature's natural affinity.

The mod includes 36 biome profiles and six natural affinities.

The intention is not to make every creature stronger. It is to make seasonal traits feel as if they belong to the creature and its environment.

For example:

• winter and cold environments naturally favor Frost;
• warm or fire-oriented creatures are less likely to adopt cold traits;
• Poison is more at home in suitable environments than in early peaceful biomes;
• strange or magical environments can favor ElementalChaos.

The creature's birth context is remembered. Moving into another biome later does not change its seasonal identity.

Optional Creature Overrides

The ecological system works with built-in defaults, so you do not need to configure every creature manually.

For players or modpacks that want more control, optional prefab overrides can customize the ecological affinity of specific creatures.

The existing allowed and excluded creature filters are also still available.

This makes it possible to tune vanilla or modded creatures without turning manual configuration into a requirement.

Seasonal Creature Names

Creatures that successfully receive a seasonal StarLevelSystem modifier also receive a seasonal title:

• Winter --- Vetrbarn
• Spring --- Várbarn
• Summer --- Sumarbarn
• Autumn --- Haustbarn

Starting with 1.3.0, the seasonal title appears after the creature's name.

Examples:

• Skeleton Vetrbarn
• Greydwarf Várbarn
• Draugr Sumarbarn
• Troll Haustbarn

The bridge does not add square brackets around the seasonal title and does not replace StarLevelSystem's own modifier names.

These titles stay with the creature that received them even after the season changes or the world is saved and loaded.

Configuration

Configuration file:

BepInEx/config/TheLionCid.SeasonalSLSBridge.cfg

Some of the main options are:

---

Setting Default Description

---

SeasonalRollChance 100 Overall percentage chance to perform a seasonal modifier roll.

DelaySeconds 0.75 Short delay before applying the seasonal modifier.

IncludeTamed false Whether tamed creatures can receive seasonal modifiers.

Each season also has configurable chances for its different modifiers.

SeasonalRollChance uses percentages, so 100 means 100% and 50 means 50%.

Version 1.3.0 also provides ecological configuration for biome influence, natural affinities and optional prefab-specific overrides.

How creatures are handled

Seasonal SLS Bridge is designed to affect new creatures, not to constantly change creatures that already exist.

The season and location used for ecological selection are captured when the creature is born.

It does not reroll a creature every time the world is loaded, when it walks into another biome, or whenever the season changes.

Players, bosses, dead creatures and traders are excluded.

Tamed creatures are excluded by default unless IncludeTamed is enabled.

This allows creatures to become part of the history of the world: a Skeleton Vetrbarn born during winter can still carry that identity when spring arrives.

Existing seasonal identities created by 1.2.0 remain compatible.

Multiplayer

The mod is designed with multiplayer in mind.

For the best experience, install the same version on the server and clients. This allows seasonal titles to be displayed consistently to players.

The server controls seasonal modifier application to avoid clients applying the same effect multiple times.

Requirements

Required dependencies:

• BepInExPack Valheim
• StarLevelSystem 1.14.0 or 1.15.0
• Seasonality

The exact Thunderstore dependencies are listed in manifest.json.

Seasonal SLS Bridge 1.3.0 explicitly supports the tested StarLevelSystem 1.14.0 and 1.15.0 versions.

Future StarLevelSystem versions are not automatically assumed to be compatible. If its public API changes, the bridge may require an update.

Installation

Thunderstore

Install Seasonal SLS Bridge and its dependencies through your mod manager.

Manual installation

1. Install the required dependencies.
2. Put SeasonalSLSBridge.dll in:

BepInEx/plugins/SeasonalSLSBridge/

1. Launch Valheim.

Compatibility and design

Seasonal SLS Bridge is intentionally a small bridge between two existing mods.

It does not:

• change creature stars or levels;
• change spawn rates;
• change loot;
• edit StarLevelSystem's modifier definitions;
• replace StarLevelSystem modifier names;
• alter Seasonality's season system;
• directly edit creature statistics.

The modifiers applied by StarLevelSystem still have their normal effects.

The idea is not simply to make creatures stronger. It is to make each season leave a believable mark on the creatures born into it, with the local environment and the creature's own nature helping shape that mark.

AI-assisted development

A significant part of this mod's development, including code generation, debugging, testing and troubleshooting, was done with the help of AI.

The author, TheLionCid, is not an experienced Valheim mod developer and is publishing this project openly so that more experienced modders can review it, identify problems and help improve it.

Feedback, bug reports and code improvements are welcome.

Permissions

You may adapt or modify this project for your own use, provided that you respect the licenses and credits of this project and its dependencies.

Do not redistribute the work of other authors as your own.

Credits

• TheLionCid --- Seasonal SLS Bridge
• MidnightMods --- StarLevelSystem
• RustyMods --- Seasonality
• BepInEx / Valheim modding community --- modding framework and ecosystem

Disclaimer

This is an independent compatibility bridge. It is not an official component of StarLevelSystem or Seasonality.

Updates to Valheim, StarLevelSystem or Seasonality may require an update to the bridge.