Eru watched the 3D projected earth-like planet in front of him, this was obtained from using the template of GOT.
The world slowly progressed under his care there was so-called Westros, Essos, Yi Ti and the different islands.He saw different places like future Valyria and Shadow lands.
He slowly sped time and watched humans slowly progressed, he saw demons and even dragons develop in places.But these beings seem to stay very close to the shadow lands.
Eru then with slight gesture of his hands moved 3D world and zoomed towards Westroes inhabited by the Children of the Forest, a diminutive species of greenseers and wood-dancers, and the Giants. The giants are primitive, wielding only tree logs as clubs; the Children are somewhat more advanced, aboriginal hunter-gatherers who make villages in the woods.
Eru smiled and said"Let's create the old gods religion."he made his avatar to decent into the world.
While in westeros the children of the forest were going about there daily lives, they were without purpose and they always come upon issues with the giants.
Who once again attacked there group,that's when they saw a massive white stag. He looked at us with great dark eyes, his silvery antlers gleaming in the half light.
All of them felt a special presence form it like it was one with nature and the next thing it did shocked them.
The white stag shapshifted into a humanoid figure,he had unfamiliar gold lines all over his body which resembled tattoos. His height was a full human arm length taller than that of an adult male and he has developed 6-pack abs.
His horns had 5; the horns are curved inward toward his head and resemble a crown.
His tattoos have also slightly changed, certain tattoos give certain buffs.His hair has turned from silver-grey to silver-white.His eyes were glowing gold.
It was Eru in different form and he just raised his hand as the trees around them come to life and attacks the giants,Another tree sticks a root into the ground. It comes up further down, tree roots enchnaced by magic grabs him and pulls multiple giants onto the ground completely subduing them.
The rest of the giant seeing this ran away, while the Children of the forest looked at the figure in awe and fear.
One of the children took the courage to walk towards Eru and questioned in there language Gerna Mohr "Who are you majestic one?"
Eru smiled, he decided to give dramatic effect as flowers started to bloom everywhere and light from the sun shined right a bow him making him look otherworldly as he said"I am the creator of these lands and even you."
This shocked all of them, while Leaf questioned"You are a god."
Eru just gave a nod and this was the start.
He taught them how to protect themselves and taught them about dragon glass and even gave them small ability to use druidic magic.
The Children of the Forest worshiped him from then on as the God of nature, Leader if the Old Gods of the Forest, and carved the faces into sacred Weirwood trees. The Children also developed great mastery of magic powers.
Later on the giants came to an agreement with children of forest and therefore no more fight occurred and Giants joined in praying to Eru.
Which got them the blessing of having better
mental capacity.
The total combined population of the Children and the giants across all of Westeros wasn't enough to fill even one of the later Seven Kingdoms, and so its vast primeval forests remained sparsely populated for many centuries.