Hwei & Leona Synergy
Hwei Mid and Leona Support win 56.2% of 3,066 Low Elo games together, +2.2 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
Leona's stuns and immobilize give Hwei a dependable window to land his control and area damage, and Hwei can keep enemies locked down after her first engage. In midgame objective fights, Leona also gives Hwei the peel and clear initiation he wants.
Playing the duo
Leona's Sunlight(P) marks enemies hit by her spells, and Hwei's follow-up damage consumes those marks for bonus magic damage.
Shield of Daybreak(Q), Zenith Blade(E), and Solar Flare(R) can hold a target in place for Hwei's follow-up control and area damage.
How to play as Hwei
Follow Leona's engage with your crowd control and area damage while the target is held still, and use your control spells to peel if she is dived. Avoid expecting a strong all-in before your early spells come online.
How to play as Leona
Let Hwei reach level 3 and have his follow-up spells ready before forcing an all-in; in midgame, use Zenith Blade(E) or Solar Flare(R) to start objective fights he can control and damage.
Sources
These notes come from r/HweiMains, checked against the champions' abilities.