The Guiding Tree is at the center of The Great Forest in the Talaxian afterlife. The deceased will meet a close family member at the Guiding Tree and be lead to a reunion with his or her ancestors.
When Neelix "died" in 2374, he didn't see the guiding tree and questioned his faith. He later imagined it in a horrific hallucination. (VOY: "Mortal Coil")