Melee allies can stack Frost for your Permafrost, keep an eye on who they are attacking.
Save Glacial Prison for encounters where you have teammates present to take advantage of it.
Use Arctic Assault to escape bad situations, interupt channeled spells or chase runners.
It takes 6 spell casts for Kassadin's slow, Force Pulse, to become castable. If he levels up that ability, judiciously use your own skills while laning against him.
Kassadin deals mostly magic damage. If he's doing well consider buying magic resist items like Mercury's Treads and Banshee's Veil.
Each time Kassadin consecutively uses Riftwalk, he pays more and more mana. Keep this in mind as you chase him.
The stats shown on this page emphasize some critical Sejuani vs. Kassadin matchup stats that can help you explain the differences between this pair of champs. For instance, Sejuani’s KDA ratio ([kills + assists] / deaths) of NaN is more than Kassadin’s KDA ratio of NaN, indicating that Sejuani may be more central to her team's team fighting effectiveness than Kassadin. This observation is largely caused by the differences in assists.
Sejuani typically has a slightly smaller longest kill spree than her enemy does. Typically, she receives more damage than Kassadin. This typically indicates differing health capacities, yet it can also imply that the champion with higher HP has less agility and thus is unable to kite away from further damage when poked or engaged.
Both LoL champions are great champions. Both champs have their pros and cons. In the game's current meta, Sejuani usually loses when playing against Kassadin, with a 48.5% win rate. Thus, Sejuani makes a bad counter to Kassadin.
While Sejuani does have a lower winrate than Kassadin, when they face off with one another, Sejuani also has a much lower difficulty level that makes her a less challenging champion to learn. You should be careful when picking Sejuani into Kassadin.
Furthermore, Sejuani also has a good amount of utility and CC, a similar amount to Kassadin. This makes her just as valuable during team fights, especially when fighting champions with a ton of burst damage.
While there isn't one best champion in League of Legends, in Sejuani vs Kassadin matchups, Kassadin is the better champion with a lower win rate, less champion complexity, and a similar amount of utility to help out your allied champions during late stage team fights.
Sejuani is a somewhat poor counter to Kassadin. You will do well by focussing your play on keeping up your CS and taking out objectives. If you are able to do that, you should be able to stand on your own as Sejuani against Kassadin.
If you would like to learn all of the intricacies of Sejuani in order to counter Kassadin during both the lane and mid / late game phases of League of Legends, you should continue reading to learn a few extra tricks and insights into this matchup. If you listen to the build and suggestions presented here, you will grow your win rate significantly and be that much closer to League of Legends pro players.
Sejuani most often racks up a lot less CS compared to Kassadin. Champs who typically don't take much CS often don't require much CS to be valuable teammates, such as sup champs. They are able to scale well off of their abilities and first items alone. Yet, champions with large amounts of CS, such as hyper-carries, often need a lot of items to be effective. In either case, try to do better than the values shown on this page to do well.
The ideal items to have in your Sejuani versus Kassadin build include Sunfire Aegis, Thornmail, and Jak'Sho, The Protean. When Sejuani used at least these three pieces in her build, she did significantly better vs. Kassadin than with many other common builds. In fact, Sejuani had an average win rate of 48.5% battling Kassadin with this build.
To have the best likelihood of annihilating Kassadin as Sejuani, you should equip the Aftershock, Font of Life, Conditioning, Overgrowth, Legend: Alacrity, and Triumph runes from the Resolve and Precision rune sets. Out of all the runes players used for Sejuani vs Kassadin counters, this set of runes yielded the best win rate. Moreover, these runes provided a 48.5% winrate overall.
If you want to see Sejuani vs Kassadin tips and counter builds for a a distinct skill level, feel free to choose one from the selection menu provided above. By default, the stats and strategies displayed are calculated using every round completed with these champs.