The base damage of his ability when he is 3-starred is 6666, a reference to "666", the Number of the Beast.
Kayn is the first Teamfight Tactics champion to be playable after having been first featured in the game as a PvE round monster, namely in Rounds 1-4 and 8-7 in Set 3 prior to his debut as a champion in Set 4.
Active - Reaping Slash: Dashes towards his target then slashes all adjacent enemies, dealing 450 / 600 / 6666 (× AP) magic damage and increasing the cost of their next spell by 33%. If the slash hits exactly one target, he immediately casts again.
Rhaast: Heals for 50% of the damage dealt by the spell.
Shadow Assassin: Deals an additional 75% damage for the first 10 seconds of combat.