Ahri vs Lux Mid Matchup
Ahri Mid wins 48.2% of 4,622 Low Elo games against Lux Mid, -0.5 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.
How to play as Ahri
Stand outside your minion wave so Lucent Singularity(E) cannot hit both you and the wave; when Lux uses E on the wave, use Fox-Fire(W) to dodge Light Binding(Q) and trade or push.
Respect Lux's stronger poke and waveclear early, then use your better all-in and roaming threat when she spends Light Binding(Q) or gives you a safe window to move.
Lux's Lucent Singularity(E) can poke Ahri and clear the wave together if she stands beside her minions; standing off the wave forces Lux to choose between the two.
How to play as Lux
Use Lucent Singularity(E) to pressure Ahri and the wave, and hold Light Binding(Q) for when she approaches to trade or commits with Spirit Rush(R).
Sources
These notes come from r/summonerschool, checked against the champions' abilities.