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.

Changelog

1.4.8

• Verified compatibility with StarLevelSystem 1.18.2.
• Future StarLevelSystem versions with a compatible public API can continue working with a single startup warning instead of being rejected only because the version number is newer.
• Real API incompatibilities still disable the StarLevelSystem integration safely and report the problem.
• The validated public StarLevelSystem API is now bound through delegates, avoiding direct calls to functions that may be absent in future versions.
• Added local seasonal icons next to creature hover names for winter, spring, summer and autumn.
• Added Titles.ShowSeasonTitle so Vetrbarn, Várbarn, Sumarbarn and Haustbarn can be hidden while keeping the seasonal icon visible.
• Added Titles.ShowSeasonIcon, Titles.SeasonIconSize and Titles.SeasonIconSpacing for local seasonal-icon UI control.
• Seasonal icons use 128×128 RGBA PNG assets and remain purely local/cosmetic: they do not modify ZDO data, StarLevelSystem state or network authority.

1.4.7

• Documentation-only update.
• No gameplay, seasonal, ecological or visual-system behavior changed in this release.

1.4.6

• Verified compatibility with StarLevelSystem 1.18.1 using a local assembly reference and contract tests.
• Added visual inheritance for BalrondHumanoidRandomizer Skeleton and Draugr variants: supported randomized variants reuse the texture set of their catalogued base creature without duplicating texture files or pulling excluded base prefabs back into the visual catalog.
• Fixed visual-property filtering so unrelated material/property blocks no longer prevent supported texture maps from being applied.
• Added a retry path when the first visual application attempt fails, with clearer warnings that include the affected prefab name.
• Big visuals are now available year-round where supported.
• Supported autumn visual variants can now act as an out-of-season fallback where appropriate.
• Visual priority remains unchanged: elemental modifiers → SoulEater → Brutal → Big.

1.4.2

• Added compatibility with StarLevelSystem 1.18.0.0.
• No gameplay, seasonal, ecological or visual-content changes in this release.

1.4.1

• Added compatibility with StarLevelSystem 1.17.0.0.
• Added new custom visual textures for the Greydwarf family.
• Added new custom visual textures for Skeletons.
• Improved and corrected several existing Troll textures for better visual consistency and UV alignment.
• Updated the public visual pack to reflect the newly completed creature families.
• Updated documentation and dependency information for the 1.4.1 release.

1.4.0

• Added the new optional creature visual system, allowing supported StarLevelSystem modifiers to have matching local appearances.
• Current public texture pack: only the Troll has fully finished custom textures for now; additional creature families will be added gradually.
• Added a visual framework/catalog prepared for 23 creature families / 38 prefabs.
• Added support for seasonal visual combinations such as FireNova, PoisonNova and winter Big.
• Added generic SoulEater and Brutal visual variants that can work in any season.
• Elemental modifiers applied directly by StarLevelSystem can now use their matching visual even when the creature has no recorded birth season.
• Added deterministic visual priority: elemental modifiers first, then SoulEater, Brutal and Big.
• Added support for body textures, eye textures, emission masks and HDR material colors while leaving unsupported or unedited properties to Seasonality.
• Added Point texture filtering by default to preserve Valheim's pixel detail, with optional Bilinear and Trilinear filtering for HD texture packs.
• Personal texture edits are preserved by the texture preparation workflow.
• Added explicit compatibility with StarLevelSystem 1.16.0, while keeping support for 1.14.0 and 1.15.0.
• The visual system is cosmetic only and does not change modifier probabilities, seasonal titles, creature stats, authority rules, spawn rates, loot or network gameplay state.
• Existing creatures are not rerolled when updating.
• Added the community Discord for mod support, feedback and contributions: https://discord.gg/kN3cqHqWYA

1.3.1

• Added support for StarLevelSystem 1.15.0 while keeping compatibility with 1.14.0.
• Improved seasonal identity persistence. Creatures now keep their birth-season identity even when they do not receive a seasonal modifier.
• Seasonal titles are now independent from modifier application, making seasonal creatures more consistent across different configurations and situations.
• Added a new optional seasonal fallback system. When a seasonal roll would otherwise result in no modifier, the creature can receive a Minor trait associated with its season:
  • Winter: Big
  • Spring: Fast
  • Summer: ResistFire
  • Autumn: Alert
• The seasonal fallback system is enabled by default and can be disabled with EnsureSeasonalModifier.
• Creatures that already have the selected modifier will keep it without receiving a duplicate.
• Improved compatibility handling with StarLevelSystem to prevent unwanted additional modifier attempts when an application fails.
• Existing ecological profiles, biome and creature affinities, seasonal probabilities, filters and multiplayer behavior remain unchanged.
• Existing creatures are not retroactively rerolled or given a new birth-season identity.
• Improved overall stability, diagnostics and testing.

1.3.0

• Added a new ecological affinity system: seasonal modifiers can now vary depending on the creature's biome and natural affinity.
• Added 36 biome profiles and six natural affinities.
• Added optional per-creature affinity overrides through the configuration file.
• Reduced Poison and PoisonNova in early-game environments, while naturally poisonous creatures can still receive them normally.
• Creatures now keep the seasonal identity of the place and season in which they spawned.
• Seasonal titles are now displayed after the creature's name.
• Added support for StarLevelSystem 1.15.0 while keeping compatibility with 1.14.0.
• Improved StarLevelSystem compatibility checks and overall stability.
• Expanded testing and diagnostics for seasonal probabilities and ecological profiles.

1.2.0

• Updated integration to use the official StarLevelSystem 1.14.0 API for safer and more reliable modifier application.
• Improved multiplayer handling so seasonal modifiers are applied only by the appropriate server authority.
• Reworked seasonal probabilities: primary modifiers now use their actual configured percentages, while secondary modifiers are selected from the remaining chance.
• Added persistent seasonal identities. Creatures that successfully receive a seasonal modifier now keep their seasonal title after saving, loading, or changing seasons.
• Added new Norse-inspired seasonal titles:
  • Winter: Vetrbarn
  • Spring: Várbarn
  • Summer: Sumarbarn
  • Autumn: Haustbarn
• Improved spawn detection so newly spawned creatures are distinguished from creatures being loaded from an existing world.
• Existing creatures are not retroactively rerolled or modified when updating to 1.2.0.
• Improved internal stability, build validation, and automated testing.

1.1.1

• Added the project's GitHub repository link to the Thunderstore manifest.
• Documentation and source repository information updated.

1.1.0

• Added seasonal visual creature titles:
  • Invernal
  • Primaveral
  • Estival
  • Otoñal
• Titles are applied without changing StarLevelSystem modifier names.
• Added cleanup when creatures are destroyed.
• Kept the stable seasonal modifier bridge architecture.

1.0.0

• Initial release.
• Seasonal weighted StarLevelSystem modifiers.
• Seasonality integration.
• Configurable roll chance, delay, tamed-creature handling and logging.