Vandi

Creatures wear more stars in a biome whose boss you keep killing, and that boss comes back harder the next time you summon it. All of it follows your own kills, not the server's.

The design is on the site, where players were asked about it before any of this existed: Stars worth earning, and bosses that remember you. Testing below says what has been checked and what has not.

Vandi is Old Norse for trouble.

The problem

Once a biome's boss is dead, that biome is mostly walking. Its creatures cannot hurt you any more, and the starred ones actually worth meeting, for the drops or for taming, are rare enough that finding one is a chore rather than an event. The usual answer is a difficulty setting, which raises the whole world for everybody at once and lands hardest on the player who has not got there yet.

The idea came from CRVD in the Discord: let the biomes you have beaten be the ones that get harder.

What it does

• Killing a boss raises the chance of starred creatures in that boss's own biome. The Elder changes the Black Forest, Moder changes the Mountains. A biome whose boss you have never beaten stays exactly as it was.
• Every repeat kill of that boss adds more: five percentage points a kill, stopping at twenty five extra. The points go on top of whatever the game already rolls where the creature spawns. That is ten in an ordinary stretch of a default world, so there a biome whose boss you have killed five times spawns starred creatures about a third of the time. The game rolls higher in parts of the world far from the centre and lower on a world set to fewer stars, and the same twenty five go on top of that. Creatures still cap at two stars: only the odds move, never the ceiling.
• Each repeat kill also makes that boss one star harder the next time you summon it, capped at two.
• All of it is yours. A player who joined last week walks into an ordinary Black Forest while the veteran standing beside them does not.

Starred creatures drop more and a harder boss drops more, so the mod pays for the trouble it makes. It is a reason to go back to a biome rather than a reason to avoid one.

The part that will start arguments

Credit for a boss kill goes to the player who made the offering, and to nobody else. They are credited even if they are dead, offline or across the map when it falls, because they paid for it. Help a friend kill their Bonemass and you get nothing from it; summon your own and it counts.

That is deliberate. Credit shared by everyone standing nearby turns a personal record into a server score, and the one promise here is that your world reflects what you have done yourself. The cost is real, and worth saying out loud: a group that always fights on one person's offerings only moves one person's world, so everyone summons their own.

Why it is not part of Utangard

Utangard already knows who has beaten what, so the boss half could have lived there. It does not, because the work is a patch on the roll that every creature spawn in the game goes through, and that is a much wider seam than Utangard's promise. Two different jobs, two mods, and either one can be uninstalled without the other noticing.

Multiplayer

Everyone will need it, at the same build. The star roll happens on whichever client owns the zone a creature spawns in, so one player without Vandi spawns ordinary creatures for everybody standing around them.

How it keeps the count

Your kills live in the world's own global keys, one per player per boss, as vandi_p_<playerid>_<bosskey> with the number as its value. Not on your character, and the reason is the credit rule above: the machine that records a kill is whichever client owned the boss when it died, and that is often not yours. The world is the one place both machines can reach.

A count is written once per boss kill, and the count keeps climbing past the fifth kill even though the boost stops there, because it is a tally other mods read, not a star level. That matters more than it looks: accepting one global key makes the server rebroadcast the whole key list to everybody connected, so a mod that wrote one every few seconds would be felt by people who do not have it installed. One write when a boss is summoned and one when it dies is nowhere near that.

For other mods

Another mod can ask how many times a player has killed a boss through Vandi.VandiApi: BossKills(playerId, bossKey), LocalBossKills(bossKey) for the player at the keyboard, and CountsKillsOf(bossKey) to check that Vandi records that boss at all. It only reads.

Use that rather than the key above. The key layout is Vandi's own business and can change, and a mod reading the key directly would then read zero kills for everyone without saying so.

Malmr, the vein mining mod, is the one that uses it. A metal's vein mining opens only once you have beaten that biome's boss at one star, which is your second kill.

What decides what, and where

• The star chance is one postfix on SpawnSystem.GetLevelUpChance, which is the single roll behind open-world spawns and every placed spawner, so camps and crypts are covered without naming them. Vandi's points are added after the game's own factors, the world's star setting and the land's multiplier, and are not scaled by either. A spawn entry can also skip the star roll altogether near the world centre (its m_levelUpMinCenterDistance), and where it does Vandi adds nothing, because the method is never called. It runs on whichever client owns the zone, and asks that client's own player. Two people standing in the same forest therefore see one answer, the owner's. A player alone in a biome always sees their own.
• A dungeon counts as the biome above it. Interiors sit directly above their entrance and biome lookups compare only x and z, so a crypt is Swamp and a frost cave is Mountain without this mod knowing what a dungeon is.
• The boss's stars are set by whichever client owns the altar, reading who made the offering, and the summoner's id is stamped on the boss itself so the credit survives the handover to a different machine.
• The kill is recorded by the client that owned the boss, from that stamp. A boss that was never summoned through an altar credits nobody.

Settings

The file is BepInEx/config/ezomic.valheim.vandi.cfg, written on first run.

On a server with Core the host's values apply to everyone, so these are the server's decision and not each player's.

Testing

scenarios/ holds two Devkit scenarios. vandi-stars-per-biome goes to the nearest Meadows, reads the star roll there, seeds a record and checks how the roll moves at each step, including that a boss from another biome changes nothing. It measures first because the roll is not 10 everywhere: in 1.0 a biome sector can carry a modifier that multiplies it, and in one Meadows stretch four kilometres out in the dev world the game rolled 20, on a world with no star setting changed. vandi in the console prints the roll where you stand and how much of it is Vandi's, which is what the scenario reads. vandi-summoner-gets-the-credit brings its own Eikthyr altar through location, so it needs only a little open ground ahead of you, most simply in the Meadows. It drives the real summoning path, because the boss half is only real through an altar.

Both passed on 2026-09-28 and again on 2026-09-29, the second time at 43 and 25 steps. On 2026-09-30 a two-player run on a dedicated server, one client summoning and killing and the other standing by, credited each boss kill once, to the player who made the offering. The one standing by gained nothing, although on that run its machine owned both bosses and wrote the credit. The scenarios for that run are Utangard's, since it checks three mods at once. What none of them covers is what a second player sees while standing in somebody else's zone.

Bugs and ideas

Both go to the site. longhouse.thijssensoftware.nl/bugs is for anything broken, and longhouse.thijssensoftware.nl/ideas is for what a mod should do next. You can vote on other people's ideas there as well.

Signing in takes a Steam or Discord account. I work from that list, so the votes decide what I pick up next.

Licence

MIT. See LICENSE.