OMF made the first tree. In the abyss of air between light and ground, he took the beams of the moon and the heat of the son and wove it with the stone and the dirt until it lightened and heated and began to shift and move in ways previously uknown to life.
At the time, most energies on the Auld were unfocused, mass clusters of raw force moving about in spastic flurries. OMF, presumably among the oldest even then, managed to focus this energy and strive for something out of the constant cycle of losing and gaining as competing spirit fields sought to absord the aether that god-forms survive on.
Willing to sacrifice itself to the storm but leave something after, OMF took his force and will and instilled it to the creation of light and clay, transforming the product that took a life of its own, drawing its energy from the soil and the sun, beginning to live independent of the aether and find the strength to grow. It was from this that Old Man Forest, then just a sprig in the ground, began to grow life on the surface of the Auldentsphere.While the original tree is lost to history, OMF is bespoken to have eyes in every forest, and at the very center of each wooded grove you will find one tree in stark ashen grey, near crumbling to the touch, said to be the beginning of growth from the energies still circulating from the sacrifice of Old Man Forest.
Homage is paid by all who rely on the forest, and OMF's presence is near undetectable in godly arenas despite his prolific presence. His origin was before gods came to be, the results of focused aether, and so OMF continues to be known as a spirit resident of the Auld. Having no voice, his desires and whims are unknown, and his action are a mystery as all but his existence can be confirmed.
Though one thing is known: that life Old Man Forest started before time began passing continues to grow.