Despite looking like a copse of vines and trees, the Boneleaf is actually an Aberration (with the plantlike traits ability). It has an Int of 8 and a wisdom of 16, making it clever enough to use its Illusionary Lure ability to cause serious "lost in the swamp" hallucinations.
Illusory Lure (Su): ...as the spell major image (7th-level caster), except that this illusion has a duration of 1d6+1 rounds, and a 1d4 round recharge. DC 14 Will save to disbelieve.
While the save DC is trash, it doesn't have a per-day limit, and between the Charnel Bog's fatigue and wisdom damaging diseases, the boneleaf has the home turf advantage.
Pervasive Sentience (Ex): ...If boneleaves are present in a given area, there are always 1d6+6 of them in the region. They are considered solitary creatures because each boneleaf in the group remains anywhere from 100 yards to a mile away from its nearest fellow...
...Anything one boneleaf experiences is known to all of them, so characters who encounter a second boneleaf after defeating the first will find it anticipates their tactics and abilities.
Put these two abilities together and you have an opportunistic ambush creature who has to be killed between 7 and 12 times, learning the party's weaknesses as it goes.
While it says the Boneleaf uses its illusionary abilities to mostly make small things like treasure to lure targets, it's entirely valid for it to create more elaborate mirages like a safe space to set up camp. It can cast it multiple times, so there's no reason it can't recast the same image, with minor changes each time as it slowly deprives the party of resources. Imagine setting up camp, setting down a pack, and the pack being replaced with an illusion...Major image hits all the senses, so there's a lot of wiggle room here.