Radiants are a select group of gifted individuals who gained hypernatural abilities as a result of the First Light event.
Following a mysterious event that affected the entirety of a near future Earth, known as First Light, select people across the globe start to gain abilities stemming from this massive event. These individuals were dubbed as "Radiants". Each Radiant has a unique set of abilities, both passive and aggressive. Most of the Agents that make up the Valorant Protocol are Radiants Like Phoenix , and others have access to Radiant technology like Breach (exactly his Mechanic Arms)
Radianite from the First Light gave Phoenix the ability to manipulate and control fire, such as his ability to throw down a Molotov-like fire or even form a fire wall with it. He can make a flare orb and blind his enemies with it. His own fire cannot hurt him, he can even heal his wound with the help of it. He probably got his nickname after his ultimate ability, he can reborn after getting killed like the ancient mythological creature: the phoenix. While using this ability Phoenix body's glowing and it's on fire. A fire/lava puddle appears at the location of the activation. This is the place where he can reborn after a short duration of time.
Radianite From the First Light gave Jett the Ability to Manipulate Wind, for example she can boost herself upwards, instantly dash in any direction on the X or Z axis, throw clouds or lift small objects and shoot them at bullet-speed.
Human or not, Omen is a radiant, and we know the Radianite gave him Abilities to teleport short distances, or long distances. He also appears to have abilities to steal enemies' sight or completely put them on Dark Shadows/Covers. Additionally, it is canon that his main Radiant ability is to come back from the void after death at the cost of being torn apart across time and space, which seems to have given him his ghostly form and teleportation
Reyna, the vampire agent was given agressive abilities like stealing enemy's sight, take a dead enemy's soul to Quickly Restore health and extra shield or become intangible, or enable an ultimate ability where her weapon skills are boosted (faster reload, weapon switch time and boosted fire rate) and can easily detect enemies as they are highlighted in a bright color.
As the Australian Eco Warrior, Skye was given the ability to control and assume animals and nature. She can heal in an AOE and in her LOS up to 100, assume the form of a Tasmanian tiger and concuss her enemy, blind enemies 3 times with a brown goshawk and can use her ultimate to locate and nearsight enemies with jellyfish like creatures.