Innate:Kayn wields an ancient, sentient weapon, that battles with him for control. Each instance of damage Kayn deals against champions (excluding damage over time) and takedowns causes them to drop orbs, red by melee champions and blue by ranged champions, that are automatically collected upon leaving combat, filling a bar around Kayn's portrait.
Once the bar is filled, Kayn can either return to the summoning platform to interact with his portrait to either be overwhelmed by Rhaast or expel him to become the Shadow Assassin, or wait 4 minutes until the other form becomes available, reduced by 5 seconds for each collected orb of their type after that.
The transformation type is decided based on the highest amount of damage dealt to the respective range type. If the two forms are within 8% of each other, the last champion range type hit will determine the transformation. The transformation will permanently change his abilities and grant him Homeguard.
Rhaast:Rhaastheals for 34.5% − 43% (based on level) of the post-mitigation physical damage that he deals with abilities against enemy champions.
The bar gets filled up completely at 500 points.
Melee orbs grant 2 points per hit and 6 points per takedown.
Ranged orbs grant 3 points per hit and 7 points per takedown.
Each bar has a bucket system.
The bucket starts at 60 points.
Each time an orb is taken the system checks if there's an amount of points in the bucket equal or higher than the amount received from the orb. If there is, Kayn is given an additional orb of the same type he received, while also subtracting that amount of points from the bucket.
The bucket fills by 0.8 points per second if out of champion combat for 70 seconds.
The amount of points received per orb is then multiplied by 3 / 6 / 10 (based on minutes).
Active: After a short delay in which he cannot perform any other actions, Kayn performs an upwards sweep with his scythe, dealing physical damage to all enemies in a line in the target direction and slowing them by 60% decaying over 1.5 seconds.
90 / 135 / 180 / 225 / 270 (+ 130% bonus AD)
Shadow Assassin:Blade's Reach'srange is increased by 200. Additionally, Kayn conjures a living shadow at the casting position to perform Blade's Reach in his stead, allowing Kayn to perform other actions.
Active:Kayn gains 40% bonus movement speed, is ghosted and can ignore terrain collision for 1.5 seconds. Immobilizing effects will interrupt Shadow Step.
Kaynheals himself upon moving through terrain for the first time and, if he's not in combat with enemy champions, Shadow Step's duration is increased. While inside terrain, Kayn's vision pierces all obstructions although cannot see into brush.
100 / 115 / 130 / 145 / 160 (+ 40% bonus AD)
7 / 7.5 / 8 / 8.5 / 9
Receiving damage from an enemy champion or dealing ability damage to them after the effect is enhanced reduces the remaining duration to 1.5 seconds. The effect also cannot remain active out of terrain for longer than 1.5 seconds and will cancel completely if Kayn basic attacks.
Shadow Assassin: Casting Shadow Step removes slows and makes Kaynimmune to them for the duration. Additionally, entering terrain will increase the bonus movement speed to 80% for the remaining duration.
Unblocked vision allows Kayn to see the full circle of his vision radius, with the exception of within brush. Note that despite not being able to see into brush, he can still see things beyond the brush.
However, enemies will be notified if nearby terrain is infested if Kayn is within 1000 units - with an indicator being placed on the terrain with a direct line between Kayn and the enemy champion. Slightly less than standard sight radius, but more than the Camouflage detection radius.
While moving in terrain, Kayn is considered dashing, so knockdown effects would stop him from moving.
Kayn can move up to 550 units beyond the outer-edge of the battlefield.
Rhaast:Umbral Trespass is modified to deal 10% (+ 13% per 100 bonus AD) of target's maximum healthphysical damage, and heals him for「 7% (+ 9.1% per 100 bonus AD) of target's maximum health 」「 70% of the pre-mitigation damage 」.