An artifact of blinding white light that acts as the foundation of the World Tree and powers it.
The Divine Stone is what powers the World Tree and supplies it with energy like a sun. It is the size of 5 human heads. It couldn't be moved with teleportation in order to prevent theft.
The Divine Stone causes the Roots of the World Tree to constantly spread through the toxic sea, absorb the toxic water, and send the toxic water towards the Pillar at a crazy rate. The Divine Stone supplies the Pillar with an enormous amount of energy to purify all the toxic waters and turn it into Nutritional Fluid to send all over the World Tree. This gives the inhabitants of the Red Zone the needed nutrition to survive.
Tekilon, the last Elvenheim King, created the Five Calamities. These Five Calamities were designed to kill the World Tree so that the Elvenheims living in the Red Zone would lose the protection the tree granted. Tekilon broke the Divine Stone into 5 fragments, each the size of a human head. He used these fragments to act as a power plant to fuel the gigantic Calamities. The fragments were inserted into the hearts and core of four of the Five Calamities; Calamity Fish, Devouring and Vomiting Roots, Ouroboros, and Wasp Legion's Queen. The last fragment was used to fuel the <Flower>, an energy barrier which protects the Elvenheim King's palace located on top of the World Tree.
The Five Relics can be inserted into the holes of the Divine Stone in order to calm down the huge amount of energy in the stone, else a person's body will blow up if one tries to control it.
The Divine Stone kept the World Tree alive and was able to supply hundreds of billions of Elvenheims with Nutritional Fluids. The Divine Stone Fragments, each the size of a human's head, were able to sustain and maintain the humongous bodies of the Calamities who's bodies couldn't live with only a single heart. Since the Calamities drank toxic water, the Divine Stone Fragments within them would convert the water into nutritional fluid and pump it towards every corner of its body.
Possessing the Divine Stone would give the user god-like powers and limitless mana. However one requires a huge amount of minute mana control in order for their bodies not to explode. If Kang Hansoo imbued the Pandemic Blade effects into the Five Relics and used the mana from the Divine Stone Fragments, he could probably kill over half the people in the Red Zone with a single slash.