For spiritual beings, death is nothing but a concept that is out of their head. It was unrelated to them as they are beings who came into existence through various complex energies in nature. And by luck and the so-called fate, they manage to manifest consciousness and in turn form their distinct personality.
That is the case for the spirit of Heart of the Forest. For centuries and thousands of years even, he lived monotonously in his designated spot while doing the job as the manager of the entire Amber Forest.
It was a smooth and uneventful life but for someone who hasn't seen much about everything in this world, that is sufficient to him… or so he thought.
Fate played jokes on an innocent tree spirit like him and just found himself losing lots of things all because of the Moon Elf Lord's actions. But that experience is also something that he greatly appreciated as this brought him to meet a "friend" that woke him up from his loneliness.