Here is the full list of all 40 FEIST achievements.
Defeat all beasts
Lure 10 ticks into a fenlight
Use all burs by the river
Defeat the three beasts in the ruins without the use of traps
Complete level 10 «playing with fire» in under 3m 30s
Complete level 10 «playing with fire» without dying
Avoid all the pit traps
Complete level 9 «ruins of the past» without dying
Complete level 9 «ruins of the past» in under 4m 30s
Complete level 8 «all good comes from above» in under 1m 45s
Complete level 8 «all good comes from above» without dying
Escape the collapsing mine without being crushed
Complete level 7 «trespassing» in under 4m 10s
Complete level 7 «trespassing» without dying
Complete level 6 «dwellers in the dark» without dying
Complete level 6 «dwellers in the dark» in under 4m 00s
Complete level 4 «down by the lake» in under 3m 45s
Complete level 4 «down by the lake» without dying
Roll a boulder over a fly
Complete level 3 «tools of the woods» in under 4m 00
Complete level 3 «tools of the woods» without dying
Complete level 2 «a picnic» in under 2m 10s
Complete level 2 «a picnic» without dying
Don't get hit by a dart trap before the cave
Complete level 1 «after a long night» in under 2m 30s
Complete level 5 «a bad hair day» without dying
Defeat the teleporting beast with a fly
Complete level 5 «a bad hair day» in under 4m 50s
Don't get squashed by a hanging weight
Free your mate
Grab a beast's fur, hold tight, and take it for a ride
Defeat a beast with a stick
Find a pine in the mine
Die during the quake after defeating a beast
Provoke an inchworm to hit another
Parry a sting projectile
Catch a fly in mid-air
Complete a chapter without eating a midge
Complete level 1 «after a long night» without dying
Free yourself from the crate in under a minute