FiddleSticks & Kai'Sa Synergy
FiddleSticks Jungle and Kai'Sa ADC win 52.6% of 2,718 Low Elo games together, +1.4 points vs expected, 2-patch window 26.19-26.20.
Researched on LoL patch 26.20. Tips are written to hold at any rank; stats come from Low Elo ranked games up to patch 26.20.
Why this duo works
Crowstorm(R) lets Fiddlesticks enter a fight from an unseen angle, where its damage can trigger Terrify(Q)'s fear across multiple enemies. That immobilization adds Kai'Sa's Plasma stacks and gives her a window to join a marked target with Killer Instinct(R).
Measured in High Elo: this duo wins 2.0pp more often than expected over 1,308 games.
Playing the duo
Fiddlesticks can fear champions by damaging them from an unseen position, and that allied immobilization contributes Plasma for Kai'Sa(P). Killer Instinct(R) can only target a visible, Plasma-marked champion within its current rank range.
How to play as FiddleSticks
Look for a Crowstorm(R) angle from fog or over a wall so the first damage fears enemies; tell Kai'Sa which target you are entering on before you go.
How to play as Kai'Sa
When Fiddlesticks' fear has marked a visible target with Plasma, use Killer Instinct(R) to join only if that target is within your current rank's range; then follow with Icathian Rain(Q), Void Seeker(W), and attacks. Q adds damage but does not add Plasma stacks.
Sources
These notes come from r/kaisamains and LoL Wiki, checked against the champions' abilities.