Seasonal SLS Bridge 1.3.1

Seasonal SLS Bridge connects Seasonality with StarLevelSystem to give Valheim's creatures seasonal combat traits.

The goal is simple: make the world feel more alive and less predictable without changing StarLevelSystem itself or replacing its own modifier names.

What's new in 1.3.1

This public release combines the fixes and improvements developed after 1.3.0 into a single 1.3.1 update.

• Explicit support for StarLevelSystem 1.14.0 and 1.15.0.
• Seasonal identity is now stored independently from modifier success.
• Seasonal titles survive empty rolls, rejected modifiers, API errors, and a 0% modifier gate.
• New EnsureSeasonalModifier option, enabled by default, provides a Minor seasonal fallback when a valid roll would otherwise be empty.
• Existing modifiers are respected and are not duplicated.
• Improved compatibility validation, diagnostics, and automated testing.

Features

Every eligible new creature stores its birth season. Season, birth biome and affinity determine the modifier profile. With the default 100% gate and EnsureSeasonalModifier enabled, otherwise empty valid rolls select a Minor backup: winter Big, spring Fast, summer ResistFire, autumn Alert. SLS must still accept the application.

Winter --- Vetrbarn

Cold-oriented traits are favored:

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

Spring --- Várbarn

Spring favors poison, adaptation and unusual mutations:

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

Summer --- Sumarbarn

Summer favors heat and aggressive elemental effects:

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

Autumn --- Haustbarn

Autumn favors lightning, poison and spiritual effects:

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

The exact result is weighted, so not every creature receives the same modifier.

Seasonal Creature Names

Eligible new creatures retain their birth-season title independently of the modifier result:

• Esqueleto Vetrbarn
• Greydwarf Várbarn
• Draugr Sumarbarn
• Greydwarf Haustbarn

The bridge does not rewrite StarLevelSystem's modifier names. The seasonal title is added separately to the creature's hover name.

Configuration

Configuration file:

BepInEx/config/TheLionCid.SeasonalSLSBridge.cfg

Available settings:

---

Setting Default Description

---

SeasonalRollChance 100 Percentage chance for a spawned creature to receive a seasonal modifier.

DelaySeconds 0.75 Delay before the seasonal modifier is applied after spawning.

IncludeTamed false Whether tamed creatures can receive seasonal modifiers.

LogAppliedModifiers true Logs successful seasonal applications.

EnsureSeasonalModifier true Fills empty valid rolls with the seasonal Minor backup, including when profile weights are zero. False restores empty rolls.

Requirements

Required dependencies:

• BepInExPack Valheim
• Jötunn
• YamlDotNet
• StarLevelSystem
• Seasonality

StarLevelSystem 1.14.0.0 and 1.15.0.0 are explicitly verified. Other versions fail the API contract check.

Installation

1. Install the dependencies listed above.
2. With the game closed, replace the old DLL with artifacts/1.3.1/SeasonalSLSBridge.dll in BepInEx/plugins/SeasonalSLSBridge/.
3. Launch Valheim.

Keep the existing configuration; the new setting is added automatically. Existing creatures are not rerolled. Only the server owning the creature ZDO applies changes; players, bosses, traders and (by default) tamed creatures are excluded.

For a Thunderstore package, the DLL should be inside the package's plugins folder.

Compatibility and design

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

It does not:

• modify StarLevelSystem's internal modifier definitions;
• replace StarLevelSystem modifier names;
• edit creature stats directly;
• require manual editing of StarLevelSystem configuration;
• alter Seasonality's season system.

The bridge waits for the creature to exist, validates the exact StarLevelSystem modifier API, and then applies one weighted seasonal modifier.

Tamed creatures are excluded by default.

Stability

If the expected StarLevelSystem API cannot be found, the bridge does not attempt unsafe internal modifications. It reports the contract problem and skips modifiers. The birth-season title is still retained.

AI-assisted development

A significant part of this mod's development, including code generation, debugging, compilation assistance 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.

If you are an experienced Valheim/BepInEx modder and see a better or safer way to implement something, feedback 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
• ValheimModding --- Jötunn and YamlDotNet
• 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.

If an update to Valheim, StarLevelSystem or Seasonality changes their APIs, this bridge may require an update.