This Must Be Done In Singleplayer. No Exceptions.
I Used This List -
https://theforest.fandom.com/wiki/Cave#List_of_CavesAnd This Map -
https://theforestmap.com/caves/Contrary To Popular Belief "Exploring Every Crevice" For Map Completion Is Not Required.
Step 1 - Go To Hanging Cave (Located In The Main Cannibal Village) And Get The Map!
- I Could Not Get Any Cave Progress To Check Off Before I Got The Map.
(Could Be A Bug, Maybe Not)
The Rest Of The Steps -
There Are Nine Total Caves To Explore. (Actually Ten Things To Check Off Though)
Found In Journal
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Explore Dead Cave
Explore Hanging Cave
Explore Wet Cave
Keep Exploring Hanging Cave
Ecplore Submerged Cave
Explore Lawyers Cave
Explore Chasm Cave
Explore Sinkhole Cave
Explore Ledge Cave
Explore Waterfall Cave
"Most Caves"
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Once The "Explore Whatever Cave" Appears In Your Journal (When You Enter It), Just Run Through The Cave Until It Is Crossed Off The List, When You Hit A Checkpoint.
The Checkpoints Are Mostly At Ropes (Climbing Spots), But There Were A Few Instances Were I Had To Go To The Parts That Usually Contain Virginias And Babys, In Order To Get Things Checked Off.
Once It Crosses Itself Off You Can Leave The Cave!
"Exploring Hanging Cave" And "Keep Exploring Hanging Cave"
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If Its Before Day 10 In Your World, Jump Off A Cliff Or Die In Some Other Way!
This Will Trigger A Cutscene.
- You Get Dragged To Hanging Cave By Cannibals, Checking Off One Of The Two Explorations For This Cave On Your Way Out!
A Friend Of Mine Got Both Of The Above To Check Off Just By Exploring It, But I Could Not And Had To Use The Get Dragged In By Cannibals Technique."Ledge Cave"
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The Checkpoint In Ledge Cave Requires You To Get The Climbing Axe And Climb Around On Some Of The Climbing Walls To Get The Cave To Check Off.
Achievement Pops As Soon As The Last One Is Crossed Off The List In The Journal.
Playing On Peaceful Does Not Void The Achievement.
Good Luck!