Thank you so much for so many thorough responses. I am shocked at how non-toxic and helpful the atmosphere is here.

My seed (the only one I played) turned out to be child's play, all the things to mistlands I embraced in close proximity. I practically didn't look for anything, the game led me by the hand. But after watching a few videos on YT I think I was mega lucky :D

Thanks to your answers, I'm already in Mistlands :)

Originally posted by Superduperlative:

Originally posted by Zep Tepi:

Sail far away from the center and look for the dark purple fog. (But don't sail off the map!)

I didn't know you could sail off the map.

If you must, do so while naked.

Originally posted by Zep Tepi:

Originally posted by Superduperlative:

I didn't know you could sail off the map.

If you must, do so while naked.

And remember to take screenshots.

Originally posted by Zep Tepi:

Sail far away from the center and look for the dark purple fog. (But don't sail off the map!)

I didn't know you could sail off the map.

Just keep swimming youll find it everntally

mistlands are the first such biome that cannot be found near your spawn -- but basically the world in V (all the worlds, all seeds that is, so YOUR world!) is a flat circle where your spawn is about in the 'center' of it, where you hang your boss heads I mean, that is your 'spawn' point. From there, you can sail a good hour in any direction and still be on the map even at top speed.
for every map, the meadows, forest, swamp, mountains, and plains can all be very close to your spawn point.
about a half hour of sailing away in any direction, the mistlands start to appear. Some maps you can walk to it on your starter island, if it happens to be gigantic, but its not normal. Most maps, you just need to set sail prepped for a long journey and with a portal you can get back home in your bag and at the home.
The other two major biomes, ashlands and deep north, are at the north and south poles and rather close to the end of the map in those directions. I recommend not exploring them much as that will block out areas you can't use when the biomes update in the future, but you can dip a toe in.
if you think roughly of 3 concentric circles around your spawn, then, the first circle has up to the plains, the second circle adds mistlands to that, and the final circle replaces most other biomes with ash/ice in the extreme north/south poles.
Its not the same as checking your map, which you may or may not want to do online, but its a very crude guide that will help you find these areas.

Sail far away from the center and look for the dark purple fog. (But don't sail off the map!)

The tree boughs of Yggdrasil up in the sky have very little to do with mistlands, and especially finding the biome.

Originally posted by Czeresiowskill:

I was sure the mistlands introduced this tree.

Nope.

Originally posted by Czeresiowskill:

And you have to enter it.

Nope.

Originally posted by Czeresiowskill:

But the further I swim, the more I'm sure it's a texture from the beginning of the game....

Yip.

Head out to roughly between 2/3 to 3/4 from the centre of the world. If you sail passed a bunch of black rocks sticking out of the sea and/or see a tonne of thick impenetrable mist (not the super thick fog weather) - that's the mistlands.

try the most eastern and western parts of your worldmap the most west and eastward the more mistlands you should find. not the north and south otherwise you generated the uninished ashlands and deep north biomes there.

another question since tc didnt say it :

you need to have parts of your wordmap that are fully unexplored for the mistlands to be generated correctly. they wont spawn on already explored areas anymore.

You may check online your maps SEED:
https://valheim-map.world/
you can see almost everything your map has on it

The tree is just decoration, its not a physical location you can travel to (although you can fall through it from above if you use a door to glitch yourself through a wall in a burial chamber). Mistlands are mostly in a circle around the spawn area starting a touch over halfway to the edge of the world, primarily to the east and west of spawn, so get a boat and a portal kit and sail east or west till you find them. Advice- land near mistlands and walk in rather than sailing in on your initial explorations.

Do you have torn spirit from Yagluth, or the wisplight? Or "Yagluth thing" as it used to be called before mistlands update.

Mistlands can be found at about 2/3 of the distance to the world's edges.