BossAdd

BossAdd adds new mechanics and phase patterns to Valheim's bosses.
Every feature is fully configurable via BepInEx ConfigurationManager (F1 key).
Supports English and Korean — auto-detected from your Valheim language setting.

Development status: Eikthyr, The Elder, Bonemass, Moder, and Yagluth are fully developed. The Queen and Fader are planned for a future update and currently only get the generic Boss Stat / Summon options shared by every boss.

Balance note: Starting with this version, each boss's default settings have been tuned to fit the difficulty of the biome it's fought in, based on extensive playtesting — rather than arbitrary placeholder numbers.

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Features

Eikthyr

• Summon — Calls minions on HP thresholds, timer intervals, or both. Includes a special elite summon at low HP.
• Stomp Lightning — Stomp attacks trigger lightning strikes with a configurable burning DoT on hit and a safe zone radius. Once active, lightning also starts crackling along the boss's own body (size and how far it spreads from the body are both configurable).
• Horn Attack — Horn charge launches players with force matching the boss's actual melee attack range. Blocked while the player is dodge-invincible. Once active, the horns themselves glow.
• Activation Effects — The first moment Horn Attack or Stomp Lightning turns on, a one-time lightning-strike visual plays on Eikthyr itself (purely cosmetic, no damage) — a little "power-up" moment to mark the transition.
• Phase Messages — Custom HUD messages at configurable HP thresholds.

The Elder

• Tree Spawn — Grows trees around players when below HP threshold. Once active, the boss's own body darkens to a charred color.
• Rock Throw Combo — The root-shoot attack triggers a configurable burst of boulder throws (count and interval), each with splash damage on impact. Once active, the boss's body stripes start glowing red.
• Activation Effects — The first moment Tree Spawn or Rock Throw turns on, a one-time visual plays on the boss itself (purely cosmetic, no damage).
• Phase Messages — Custom HUD messages.

Bonemass

• Split Summon — Splits into 5 MiniBonemass variants at HP threshold.
• Kill Condition — Bonemass cannot die until all 5 MiniBonemass are defeated, in a set color order (configurable). Minis out of order still take damage normally, but a hit that would kill one instead "saves" it at 50% HP and heals Bonemass itself a bit (configurable), with a message and a visual effect at Bonemass's own position. Optionally, Bonemass itself can be made fully invulnerable (including to damage-over-time) while any mini is still alive. Fully synced in multiplayer — every player sees the same order enforcement and healing, not just the host.
• Mini Stats — Customize MiniBonemass HP, damage, speed, attack range, and damage resistances independently.
• Mini Leash — Minions that wander too far from the main body are teleported back near it, so they can't be kited away indefinitely (configurable distance).
• Always-Visible Nameplates — MiniBonemass names are always shown, not just when directly aimed at.
• Throw Summon — Throw attacks have a chance to spawn additional minions. The throw attack itself can now be blocked with a shield.
• Phase Messages — Custom HUD messages.

Moder

• Air Breath — Fires frost breath while airborne. Deals damage continuously for the duration of the breath (tick rate, duration, damage, and knockback all configurable) instead of a single hit, can be blocked or dodged throughout, and staggers you on a solid hit. Once active, Moder's fur takes on an icy blue tint.
• Ground Breath — The dragon's grounded breath attack works the same way — continuous multi-hit damage for as long as the breath lasts, blockable/dodgeable the entire time, and staggers on impact.
• Dragon Shockwave — Landing (and now taking back off, too) sends out an expanding shockwave ring that follows the shape of the ground. Anyone caught in it takes blunt damage and gets knocked back — blockable (still knocks you back even through a shield) and fully avoidable with a well-timed dodge-roll.
• Dragon Fear — The roar now telegraphs a lightning strike aimed at wherever you're standing the moment it starts. Move away before it lands and you take nothing; get caught and you're struck by lightning and left briefly slowed — a shield won't stop the slow, but it does reduce the direct damage. Once active, Moder's horns glow.
• Activation Effects — The first moment Air Breath or Dragon Fear turns on, a one-time lightning-and-impact visual (sized to Moder) plays on the boss itself (purely cosmetic, no damage).

Yagluth

• Whipping Beam Breath — The breath attack now whips side to side while tracking nearby players, hitting repeatedly instead of just once (fire rate configurable). Dodge-rollable throughout, and blocking cuts the impact damage but not the burn.
• Curse of Enervation — A palm slam sends out an expanding red ring. Jump or roll away to avoid it — getting caught drops your HP to a set percentage and leaves you Encumbered (no running) for a while.
• Empowered Meteors — More meteors fall from the sky, and they fall faster.
• Threshold Warnings — A HUD message announces when an attack gets empowered as Yagluth's HP drops. Once an attack is empowered it stays that way even if Yagluth heals back up afterward (can be turned off).
• Yagluth's Gaze — At a set HP threshold, Yagluth roars and summons four glowing heads, each a different color. Kill the one matching the color glowing on Yagluth's own body to break its invulnerability. Guess wrong and that head dies, nearby players are left Encumbered, and Yagluth heals a little; run out of the time limit (5 minutes by default, shown counting down above the heads) and Yagluth heals instead of taking the hit. Get it right on the very first try and Yagluth is struck down by lightning, left helpless for 10 seconds. While active, the heads close in on players and fire beams of their own.
• Removed the Skeleton Warrior Summon mechanic.

The Queen

• HP Summon — Spawns brood at configurable HP intervals.
• Timer Summon — Spawns brood on a repeating timer during combat.
• Breath Summon — Breath attacks trigger additional minion spawns.
• Poison Field — Creates persistent poison damage zones along her movement path.

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Changelog

v1.2.2

Fixed

• Eikthyr — So... I added a feature that cleans up Eikthyr's summoned monsters when a player dies, and it turns out it wasn't working right! It was also wiping out every creature of the same type nearby — tamed animals included (sorry, little boars 🐗). How did I find out? I read BossAddFix by HotdogKnights, haha! This cleanup has been removed: Eikthyr's summons now stay until someone kills them or Eikthyr itself dies, just like the other bosses — and BossAdd only ever removes monsters it actually summoned, never tamed or wild creatures. Big thanks to HotdogKnights — you no longer need BossAddFix from this version on. (This affected 1.2.0 and 1.2.1.)

v1.2.1

Development status: Eikthyr, The Elder, Bonemass, Moder, and Yagluth are now fully developed. The Queen and Fader are planned for a future update. Also starting this version, every boss's default settings have been retuned to fit the difficulty of the biome it's fought in, based on extensive playtesting.

New

• Eikthyr — Horn Attack now makes the horns themselves glow once active; Stomp Lightning now makes lightning crackle along the body once active (size and spread from the body both configurable).
• The Elder — Rock Throw now tints the body's stripes red once active; Tree Spawn now darkens the body to a charred color once active.
• Moder — Air Breath now tints the fur icy blue once active; Dragon Fear now makes the horns glow once active.
• Eikthyr / The Elder / Moder — New "activation" effect: the first moment one of the above abilities turns on, a one-time cosmetic visual plays on the boss itself (purely visual — no damage, knockback, or status effect to the boss or nearby players). Never repeats for that boss, even for players who join or reconnect later.
• Settings menu — Item display names now switch between Korean and English immediately when you change your in-game language and reopen the F1 menu (previously required a full restart — mouse-over descriptions still do). A thin divider line now separates each ability's settings within a boss section.

Changed

• Bonemass — Reworked the mini kill-order gimmick: out-of-order minis are no longer invulnerable — they take damage normally, but a hit that would kill one instead saves it at 50% HP and heals Bonemass a little (configurable) instead. The rescue message and visual effect now play at Bonemass's own position instead of the mini's.
• Yagluth — Yagluth's Gaze now triggers by default at 5% HP (previously 50%).
• Packaging — AnimationSpeedManager is now merged directly into the main plugin file instead of shipping as a separate DLL, so anti-cheat mods no longer mistake it for a suspiciously-loaded runtime assembly.
• Numerous per-boss default values were retuned to match actual biome-appropriate difficulty (see Development status above).

Fixed

• Bonemass — The "stay invulnerable while any mini is alive" option now also blocks damage-over-time effects, not just direct hits (DoT could previously bypass it entirely).
• Moder — Dragon Fear's melee-range detection could misjudge "near the boss" for large boss sizes, causing its kiting-compensation timer to trigger incorrectly.
• Yagluth — Meteor attacks could occasionally be missing attacker ownership info; the head-pattern invulnerability could occasionally be bypassed by certain damage sources.
• The Elder — Fixed Rock Throw's impact visual defaulting to an effect name that doesn't actually exist in the game.
• All Bosses — Fixed boss-summoned-monster death/cleanup effects sometimes not playing, or occasionally getting stuck and never disappearing, due to timing issues with how the effects were cleaned up.
• All Bosses — Fixed a rare "Destroying components immediately" error that could occur during VFX cleanup.

v1.2.0

• Yagluth — Full attack overhaul: a new whipping, player-tracking beam breath; a curse-ring slam that saps your strength if it catches you; empowered meteors (more of them, falling faster); and HUD warnings whenever an attack gets empowered.
• Yagluth — New attack, "Yagluth's Gaze": four glowing heads appear and you have to kill the one matching the color glowing on Yagluth's own body to strip away its invulnerability. Guessing wrong, or running out of the time limit, heals Yagluth a little instead; guessing right on the very first try leaves it struck down and helpless for 10 seconds. Removed the old Skeleton Warrior Summon mechanic to make room for this.
• Moder — Dragon Shockwave now also triggers when taking back off, not just when landing.
• Moder — Dragon Fear's roar has been reworked: instead of the old stun effect (which wasn't working), it now telegraphs a lightning strike aimed at wherever you're standing — move away in time and you avoid it entirely.
• All Bosses — Fixed the movement speed and attack speed settings not doing much of anything. Movement speed now properly affects every way a boss can travel, including Moder's flight; attack speed now visibly speeds up the attack motion itself instead of just shortening the pause between swings.
• All Bosses — Boss-summoned monsters now appear with a short summoning-circle effect at a random spot near the boss instead of popping in instantly, and the summon is cancelled outright if the boss dies while the effect is still playing. This now also applies to Eikthyr, which previously had its own separate (unanimated) summon handling.
• All Bosses — When a boss dies, any monsters it had summoned now go down in a short effect of their own shortly afterward, instead of being left standing around. Eikthyr included.
• All Bosses — Special Summon now plays the same summoning-circle effect as a normal summon, but 3x larger, so you can tell at a glance that something bigger is about to show up.
• All Bosses — Fixed several boss-summoned monster types that were still dropping loot on death — summoned monsters are never meant to drop items, and now none of them do.
• All Bosses — If the same summon trigger fires again while a previous summon's appearance effect is still playing, it's now correctly counted against the summon cap — previously the cap could be briefly exceeded this way.

Settings changes (for server operators)

• New per-boss settings: Summon Spawn Radius and Summon Spawn Delay, controlling the summon-appearance effect above. Eikthyr now has its own copies of these two (previously summon-only, no appearance effect at all).
• New per-boss setting: Special Summon Spawn VFX Scale (default 3.0) — how much bigger the Special Summon's appearance circle is compared to a normal summon's.
• Removed: the old Special Summon Effect setting (for every boss, including Eikthyr's — replaced by the new summon effect above), Yagluth's old Skeleton Warrior Summon settings, and a few leftover internal/debug settings from earlier Yagluth test builds.
• Any old settings left over from a previous install are simply ignored now — safe to delete from your config file if you want to tidy it up.

v1.1.1

• Valheim 1.0 — Re-validated the entire mod against the official Valheim 1.0 release and confirmed compatibility.
• Eikthyr — Lightning Strike can now be blocked with a shield.
• Eikthyr — The burning effect from Lightning Strike now goes out normally when you get wet or stand in the rain, instead of never extinguishing.
• The Elder — Boulder Throw now knocks players back on impact.
• Bonemass — The ooze throw attack can now be blocked with a shield, and hit accuracy has been significantly improved.
• Bonemass — Blocking the ooze throw still applies the "Filthy" slow effect even on a clean full block — only the damage is reduced, the slow always goes through.
• Bonemass — Fixed Mini Bonemass kill-order enforcement not actually working — attacking them out of the required color order no longer results in an unintended kill.
• Bonemass — Mini Bonemass nameplates now display correctly for every player, not just the host.
• Bonemass — Minions that wander too far from the main body are teleported back near it, so they can't be kited away indefinitely.
• Moder — Removed the Frost Clone and Ice Field mechanics entirely.
• Moder — Ground Breath and Air Breath now deal damage continuously for as long as the breath lasts, instead of registering only a single hit no matter how long the animation played. Blockable and dodgeable throughout, and now cause a stagger reaction on hit.
• Moder — The landing roar has been reworked into "Dragon Fear" — failing to dodge it inflicts a brief Stunned status effect. (Not working correctly at the time of this release; replaced with a different ability in a later version — see above.)
• Moder — New attack on landing: "Dragon Strike" — an expanding shockwave ring spreads out from the landing spot and follows the terrain's shape naturally. Blockable (still knocks you back even when blocked) and fully avoidable with a well-timed dodge-roll. A stomp impact effect plays the instant Moder touches down.

v1.1.0

• Moder — Ground Breath and Air Breath now deal damage continuously while the breath is active, instead of registering only a single hit no matter how long the breath animation played. You can block them with a shield or dodge-roll through them at any point during the breath.
• Eikthyr — Lightning Strike can now be blocked with a shield and properly knocks you back (the knockback was silently broken before and never actually pushed anyone).
• Eikthyr — The burning effect from Lightning Strike now goes out normally when you get wet or stand in the rain, instead of never extinguishing.
• The Elder — Boulder Throw impacts (both the direct hit and the splash) now properly knock players back.
• Bonemass — The ooze throw attack can now be blocked with a shield.
• Bonemass — Fixed a rare case where a single massive hit could kill Bonemass outright and skip the minion-split phase entirely, making the fight impossible to finish normally.
• Bonemass — Mini Bonemass kill-order enforcement (and the healing penalty for breaking it) now works correctly and consistently for every player in multiplayer, not just the host.
• Bonemass — Fixed non-host players occasionally getting kill credit/experience for Bonemass without the fight actually being finished.
• Bonemass — Mini Bonemass nameplates are now always visible instead of only flashing briefly when directly aimed at.
• Bonemass — Minions that wander too far from the main body are now teleported back near it, so they can no longer be kited away indefinitely.
• Bonemass — Fixed a bug where reloading mid-fight (e.g. after a disconnect or crash) could leave Bonemass permanently unkillable; it now automatically detects and recovers from this on its own.
• Stability — Boss mechanics are now isolated from each other, so a problem in one no longer silently prevents other mechanics (or even basic respawn checks) from running that frame.

v1.0.5

• Bonemass — MiniBonemass now only uses melee attacks. Poison gas and the throw attack are no longer given to it, which also improves performance (fewer active status effects/projectiles).
• Bonemass — MiniBonemass now gets its own dedicated weapon data instead of sharing Bonemass's, so the attack range and attack interval multipliers actually take effect (previously had no real effect on behavior).
• Bonemass — New gimmick: while any MiniBonemass is still alive, the main Bonemass takes no damage (configurable on/off). Hit effects and sounds still play so it's clear the hit didn't count.
• Bonemass — Throw attack overhaul: the ooze blob now uses an exact parabolic trajectory that reliably lands on the targeted player, with configurable projectile speed, blunt/poison damage, and hit-detection radius.
• Bonemass — New status effect ("Filthy"): a successful throw hit now applies a movement-slow debuff, with configurable duration.
• Bonemass — Throw Summon (bonus monster spawn on throw) now spawns at the projectile's actual impact point instead of around the player, so it lines up with where the ooze actually landed.
• Multiplayer — Fixed MiniBonemass (split clones) and MiniModer (frost clones) not appearing at all for non-host players.
• Multiplayer — Guests can now see and fight clones normally instead of them silently failing to sync.
• BossStat — Fixed HP multiplier stacking across sessions/zone reloads for a persisted boss, which could make bosses effectively unkillable over time. It's now always recalculated from a cached original prefab value instead of the current (already-modified, possibly-saved) one.
• BossStat — Fixed the HP multiplier not applying to bosses summoned via the boss altar (it worked when spawned via console command, but not through normal altar summoning).
• BossStat — Fixed the attack speed multiplier not actually changing how often a boss attacks — it now correctly affects the weapon's real attack cooldown, not just an unused internal floor value.
• Eikthyr — Fixed the lightning attack's burning DoT applying even when the lightning strike itself was dodged. It now only applies on an actual hit.
• Stability — Fixed an issue that could cause infinite loading in certain situations, caused by a stale object reference left behind during VFX cleanup.
• Stability — Fixed several runtime exceptions that could stall combat hit detection or prevent monsters from equipping their weapon correctly.

v1.0.4

• Eikthyr — Removed the Fire Patch mechanic entirely.
• Eikthyr — Horn Attack launch range now matches the boss's actual melee attack range instead of a separate config value.
• Eikthyr — Horn Attack no longer launches players while they are dodge-invincible.
• Eikthyr — Removed the lightning telegraph (warning) delay and the lightning slow (shock) effect. The lightning burn DoT is unchanged.
• Eikthyr — Fixed a crash in Horn Attack caused by accessing a private ZNet field directly.
• All Bosses — Fixed a serious bug where HP, movement speed, and attack speed multipliers kept stacking every time a boss's zone reloaded (e.g. after a player died or reconnected mid-fight), eventually making bosses effectively unkillable or hyper-aggressive. Multipliers are now always calculated from a cached original value instead of the current (already-modified) one. Affects all 7 bosses.
• The Elder — Rock Throw is no longer an independent cooldown/chance-based ability. It now triggers as a configurable burst combo (count + interval) whenever the root-shoot attack fires.

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Requirements

• BepInEx for Valheim
• MonsterDB — required for Bonemass's Mini Split mechanic. Installed automatically as a dependency. The 6 Mini Bonemass creature definition files are bundled with BossAdd and install automatically to BepInEx/config/MonsterDB/Import/; if installing manually, make sure they end up in that same folder.

Compatibility

Most boss modifications (size, HP, damage, resistances) are handled internally via config values and don't need any other mod.

Note: Using BossAdd together with monster stat mods such as CLLC (CreatureLevelAndLootControl) may cause stat conflicts on Mini Bonemass. This is not officially supported.

Installation

Install via r2modman or Thunderstore Mod Manager (recommended).
Manual install: extract to BepInEx/plugins/bossadd/.

Configuration

Open the F1 menu in-game to adjust all settings per boss.
All features can be individually enabled or disabled.
Each boss gets its own section, with each ability's settings grouped together and separated by a thin divider line, so related options stay easy to find.
Config file: BepInEx/config/bossadd.cfg

Language Support

Setting item names in the F1 menu automatically switch to English or Korean based on your current Valheim language — change the language in-game and reopen the F1 menu to see it take effect immediately, no restart needed.
Mouse-over descriptions, however, are only set once when the game loads, so those still need a full game restart to switch language.

Bug Reports & Support

Found a bug? Please report it so it can be fixed!

When reporting, please include:

• What happened and what you expected
• Your mod list (other mods installed)
• The BepInEx log file (BepInEx/LogOutput.log)