Rengar & Syndra Synergy
Rengar Jungle and Syndra Mid win 45.1% of 1,719 Low Elo games together, -0.0 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.
Playing the duo
Rengar's leap gives Syndra a clear opening to land Scatter the Weak (E), and Syndra's Unleashed Power (R) can finish a target who survives Rengar's burst.
How to play as Rengar
Use Thrill of the Hunt (R) when Syndra can follow from nearby; her stun and burst make the marked target harder to escape after you leap.
How to play as Syndra
Hold Scatter the Weak (E) for the target Rengar jumps on, then use Unleashed Power (R) if they escape his first burst at low health.
Sources
These notes come from r/Rengarmains, checked against the champions' abilities.