I just started playing 2 days ago. On the first day I ended it thinking the game wasn't going to be too much different than playing Minecraft or Rust really, and my main point of thinking this was just that the environment wasn't tooooo much of an issue if I just played safe and coasted through whatever power progression
Then on the 2nd day I met my first troll in the Black Forest and WOOW that changed everything. I was just mining copper in the woods not too far from my nearby camp and then a huge grunt rattles my earphones, so I turn around to see that big blue looking mf running toward me with his club. My first thought was "Ohhh wow! That's cool! A big slow enemy that I'm just gonna out-manuever to get easy damage like a really slow Dark Souls boss. No biggie." Then I saw that man swing once and OBLITERATE 5 huge trees, 2 of which almost fell on me and clobbered my ass. I wasn't scared because I could die and lose all my stuff, I was immediately TERRIFIED because I imagined those 5 huge trees instead being my tiny cabin I'd been spending hours building. And that's when the fear for the environment actually set in. I ran away in the opposite direction of my house and after probably 5-10 minutes I had lost it and circled back around to my base. And running from them with low stamina was pretty hard, it forced me to use the terrain a lot.
From there it was straight serious, meticulous preparation solely for needing to kill that thing or at the very least keep it away from my house. I chopped down a bunch of big trees but left them lying down in a huge area around the mini meadow my cabin was nested in within the Black Forest so that it created a big obstacle maze of logs that'd slow down the troll, thinking back to how I saw it struggle to get around terrain while previously running away. I quickly went from only having a stone axe and flint spear as weapons and no armor to having a bow, fire arrows, bronze arrows, bronze spear, and a full set of leather armor. I had my stamina food setup optimized for maximum stamina to keep running away. I was ready.
Then I woke up one day and heard a troll nearby and knew it was go-time. Quickly got my invetory ready and sprinted out to find it and lure it away from the house. Now this is the part of the game where this solidified it as the best survival experience I've had since Minecraft in 2011. Luring the troll away while juking it out around all the trees I had fallen while turning to shoot and parkour with the trees and green rushing past the screen, it all felt like I was in a movie in a way no game has before. Was amazing. The ability to manipulate the terrain in a realistic way for prepping for a fight like that is something I haven't ever seen a game nail like this one did.
After some more high octane action sets through the woods, I finally killed that dude and wore his forehead skin as a hood. 11/10 Game.
Source: https://www.reddit.com/r/valheim/comments/zk8orx/my_first_troll_encounter_changed_how_i_look_at/