The Green Man (Full name Oran Porpherio) was the keeper of Porpherio's Garden in the Feywild
Roughly 2 or 3 thousand years ago, Oran Porpherio was a gardener with a nomadic tribe. It was his job to raise plants for food wherever they moved. However, his gardens were not very long lasting, as soon as the fruit bloomed, they were harvested, saved, and the tribe could move on. Porpherio prayed that he could use his gardening talent for something greater, praying to the heavens (and the old gods) for an answer.
After a tribal fight, Porpherio was left behind in the mud while his tribe fled. Instead of being massacred by the rival tribe, Porpherio's prayers were answered. Just as he was about to be skewered, the ground opened up beneath him, swallowing him whole. And when he awoke, he found himself in a massive underground cavern, full of natural sunlight and grass, but few trees. The Goddess Mielikki spoke to him, telling him that she had heard his prayers, and had mystically created this pocket space that he could spend his whole life gardening. However, the mystical properties disjointed the space with the rest of the realm, placing it at 700 times slower than the real passage of time. Those who slept in the garden a day found themselves a year in the future when they left, and those who spent years in the garden emerged in worlds completely unlike the ones they left.Porpherio emerged once every 500 years, bringing with him new plants he had bred and invented, and during those times, the passage remained open, where various plants and trees managed to fall into the passage, trapped forever in Mielikki's pocket garden for Porpherio. Porpherio himself spent so much time tending to his garden that he eventually became part of it, Mielikki granted him demi-god like powers to take care of the plants of the world from a material point of view. Now the "Green Man", he took great pride in the plants of his garden, as well as the new fauna that had fallen in over time.