Yone & Sejuani Synergy
Yone Top and Sejuani Jungle win 52.2% of 2,514 Low Elo games together, -0.1 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
Yone's melee basic attacks apply Sejuani's Frost stacks, helping her reach Permafrost(E)'s stun threshold; Sejuani players specifically list Yone among the allies who can build those stacks quickly.
Sejuani players describe an R-to-R combo with Yone: Glacial Prison(R) stuns its first champion hit, and Fate Sealed(R) can follow through that target and pull any other enemies caught in its line.
How to play as Yone
Follow Sejuani's Glacial Prison(R) with Fate Sealed(R) through the stunned target; aim through nearby enemies too if they are lined up for the pull.
How to play as Sejuani
When Yone is close enough to follow, add Winter's Wrath(W) stacks and let his melee attacks help build Frost before you use Permafrost(E) on the fully stacked target.
Sources
These notes come from r/sejuanimains, checked against the champions' abilities.