"We are one. We are many. We are Legion."
-Legion, the Dread Symbiote
Whoever Legion was before he got infected remains unknown up to this day. But what we do know is that its sole purpose is to kill. The creature that infected Legion and made a home in him came from the void. Much like Cho'gath or Kog'Maw. These creatures are called Zar'Dors. Zar'Dors are natural predators that have advanced senses of sight, smell and hearing. There have been several recorded accounts of Zar'Dor related incidents. Most leading to the death of the host. But Legion is the only recorded Zar'Dor to fully manipulate a human host and use its body as its own. Eventually, Legion made his way into the League of Legends, seeing that the several battles will satisfy his desires.
Killer Instinct (Passive)
When Legion is hidden in a bush, nearby enemy champions are visible on the map.
Malicious Gnaw (Q)
One of Legion's symbiotes bite an enemy unit in front of them, dealing physical damage and reduces their armor by 8/9/10/11/12%. Legion also heals himself for a portion dependent on his maximum health. When he kills an enemy unit with this ability, half the mana cost is refunded.
Vicious Swipe (W)
Legion does a 180 degree swipe with his left arm, hitting all enemies in front of him and applies continuous physical damage over time for 4/5/6/7/8 seconds, with each tick dealing 2% more damage than the last.
Predatorial Camouflage (E)
Passive: When Legion remains idle for 5 seconds, he turns invisible and gains bonus movement speed for 3 seconds. Movement will not disrupt the invisibility. The next basic attack while invisible will deal bonus physical damage.
Symbiote Drone (R)
Legion spawns a Symbiote Drone and hurls it at an enemy, attaching itself to whoever it hits. The Drone sucks life force from the enemy, dealing true damage for 6/7/8 seconds. The Drone is also linked to Legion, healing him for the same amount of damage being dealt to the enemy. The Drone explodes afterwards, dealing magic damage to both the host and all enemy units around it.