(Matumada)|items = Esteemed Heirloom
Sun Flower}}The Radiant Stone is a radiant orange-yellow cube found on the center of Radiant Isle in Matumada. The Radiant Stone's heat will damage players the closer they get to it, quickly killing even the most armored adventurers who pass too close to it. It is advised to take caution when near this landmark.
The Radiant Stone has a secret feature that originally went unnoticed by the community of Fantastic Frontier that lasted for four days before it was revealed. In order for the secret feature to be revealed to the player, the player must stand close enough to the cube to feel the radiation aura it produces for an approximate time duration of 25 seconds before an explosion will occur. The explosion will not kill the players and simply indicates that the player had received something from the Radiant Stone. Possible rewards that can be obtained from the Radiant Stone Challenge can be seen below:
- Esteemed Heirloom
- Genie's Rings
- Gold Ore
- Lumoore Mushroom
- Radiant Medallion
- Radiant Sapling
- Sun Flower
It is heavily advised for players to have some sorts of HP Regen-based equipment or any armor sets that provide around 70 armor points and above to counteract the intensity of the radiation emitted from the stone. In addition, it is also advised for players to have some sorts of methods to quickly move away from the cube once they get a reward, whether it's to parasail away from the stone or sprinting as quickly as possible to a safe spot. Consumables such as Rich Man's Delight, Stone Slime, Divine Grapes, and Dungeon Candies are the players' best friends to survive the Radiant Stone Challenge in order to restore their HP each time they are hurt by the radiation of the stone.
- Right after the Spring Update was released, the Radiant Stone had been a focus of many experimenter and secret-hunters due to the mysteriousness of the object.
- Standing on the edge of the damage zone will not allow you to gain an item after the 20 second timer, as you have to be closer to the aura.
- It is possible to still get the reward while dead, resulting in you respawning with whatever you won in your inventory.
- Rewards given to players after successfully surviving the Radiant Stone Challenge either meets one or more of the following requirements:
- They are orange.
- They are yellow/golden.
- They glow/radiates yellow light/energy.