A PC who succeeds at a DC 10 Nature or Religion check recognizes that the spirit needs a host to
interact with the living world, and wants to possess a PC in order to share its experience; these types of spirits are not strong enough to take control of a body they possess, but they may influence their host’s thinking and behavior by superimposing their own consciousness.
If the PCs wish to avoid being possessed, they can easily circumvent the slow-moving spirits and be on their way. If a PC chooses to accept a spirit into their body, however, they experience a rush of memories, both from the spirit’s living days and its recent moments roaming the forest.
First PC to Volunteer (open spoiler)
Second PC to Volunteer (open spoiler)