Here is the full list of all 13 Dark Forest achievements.
Take a 1000 yd shot
Kill 1000 monsters in the same game
Kill 500 monsters in the same game
Kill 100 carnivorous plant
Destroy 100 eggs before hatching
Kill 4 enemies with a single lightning
Kill 4 enemies with a single use of guided magic.
Kill 10 enemies with the same slow motion
Kill the mini boss Giant Eye
Kill the mini boss without losing any life
Survive at least 10 minutes
Kill 10 necromancers before summoning skeletons