I'm a big fan of the invasion events (in any game really) because it throws you off the normal routine and this is just me thinking out loud & rambling about ideas how to add an additional layer of events to give as unique experience as possible and empowering the illusion of a living world within Valheim. If the developers ever find themselves running low on ideas 8) Also features some general ambience ideas.

All these events should have a radius where's the least occurance happends in the middle of the map (starting point), while it increases the further away from the middle you travel (I'm thinking something like this https://imgur.com/a/AjkF2nz). Because when you start out everything is exciting, but as you progress you want new things to happen. This would encourage/make it a bit more exciting visiting new locations that are of the same biome.

Feel free to add your own suggestions in the comments, I might try to update this list as time goes. Personally I still hold this game as the game of the year. Well done Iron Gate!

Random events:

Helper fox – (rare) – [Black forest, Mountain]

He will spawn nearby but out of visible range.
He will stay around you for a bit and if you start following him, he will guide you to:
- If you are full health, he will guide you to a big area of interest (ore, unopened loot chest, unvisited dungeon, village, merchant)
- If you are a brand new player/just started, he will guide you to basic stuff like flint etc.
- If he senses that you are low on health, he will guide you to nearest food (berries, crops).
He will never go a straight path to the area. It should be more like a random S-shape path so you don't always know if he is helping you or not.
It should be random if he actually will help you or not.
It should be possible to attack him but then he will not help you. He will not fight back just run away.
If you come close enough to his area of interest it will end the event and put the fox in idle/general mode.
Sound idea when he wants your attention: https://youtu.be/vGZwN_xCRcg?t=120
If tamable he should still be able to guide you to interesting stuff but with a major reduction in incidence. Like a 4-hour timer to avoid spammy behaviour. If you don't start follow or give him any attention within 10 min he will go back into idle/general mode.

Bird flock – (common) – [All biomes]

Just for ambience
Birds in different formations flying in the sky https://upload.wikimedia.org/wikipedia/commons/0/0b/Eurasian_Cranes_migrating_to_Meyghan_Salt_Lake.jpg
Should they fly in a certain direction that there will be a area of interest?

Bats – (common) – [Dungeons, Tombs]

A group of bats will fly against you and quickly disappear (scare moment)
Trigger event when opening door or just anywhere when in a narrow tomb passage

Big viking warship – (unique, once per world) – [Seas]

This can be played out as:
- A) An animation of a ghost warship crashing/capsize in the sea infront of the player and then transitions to a static shipwreck below sea level/or slighty below sea level so it's accessible.
- B) A static event. A big shipwreck (much bigger than the ones already in game) located on a remote island.
- C) Event will only trigger when player is far out on sea. Ship will spawn in distant and is slowly sinking, you will have to get there in time to be able to loot it, after this the shipwreck will settle on bottom of the sea and will never be accessible again.
The shipwreck should carry a treasure chest with a unique item, perhaps like a cloak/specific tool that once was owned by a powerful legendary viking?

Beaver – (extremely rare) – [Meadows]

Spawns near lakes and rivers
This one will go ham on trees, watch out!

Draugr Pirate Ship/Ghost ship – (rare) – [Seas]

Will only spawn during night
A small ship with a few Draugrs and their captain that will start attacking you and your boat!
Credit https://old.reddit.com/r/valheim/comments/n4g75t/simple_idea_draugir_ships_on_seas_outside_swamp/

Porpoise/Tumlare lighty jumping/sea surfing – [Seas]

Just for ambience
Common sight in north parts of norway and svalbard

Squirrel

Just for ambience

Sleeping Troll – (rare) – [Black forest]

Loud snoring

Troll giving another Troll a ride on a cart – (one-time event per world) – [Black forest]

Would be a fun sight

Travelling merchant – (rare) – [All biomes]

Will be available as event first after XX days has gone.
Will spawn nearby user-built buildings but out of visible range.
Old man/lady with cart
Will walk closely to your buildings and stay for a little while then continue their journey until out of visible range and despawn.
Has different items for sale than the regular merchant. Atleast one unique ability item. Then perhaps some prebuilt things like iron torch/sconce. Or maybe a telescope (credit https://old.reddit.com/r/valheim/comments/pnj0a8/idea_for_new_merchant_item_binoculars/)

Volcano Eruption – (extremely rare) – [Ashlands]

Wandering boss(es) – [All biomes]