Kassadin's ultimate has many uses and is on a shorter cooldown than most, use it often.
Kassadin has multiple item paths; he can go caster via Mana and Ability Power or anti-caster with Cooldown Reduction and Magic Resist.
Try to get the Ancient Golem buff to counteract Riftwalk's increasing Mana cost.
Use Demacian Standard as a scouting tool when worried about incoming enemies.
You can use the Dragon Strike / Demacian Standard combo to get out of your own Cataclysm arenas.
Split your basic attacks on different champions at the beginning of fights to maximize damage.
The Kassadin Jarvan IV synergy stats shown here demonstrate the areas of his gameplay that do better (or worse) when paired with Jarvan IV, compared to his overall stats. Significant differences are areas of focus that highlight how his gameplay changes when paired with this other champion.
Overall, Kassadin sees a very large drop in his KDA (ratio of kills and assists to deaths) when paired with Jarvan IV. His KDA went down from NaN to NaN. This negative change shows that Jarvan IV helps Kassadin perform worse in competitive LoL rounds. Yet, the small difference shows that this performance change is only marginal.
When Kassadin tries to synergize with Jarvan IV, he sees a small increase in his total damage dealt. This change may signal that Jarvan IV supports by providing cover for him to deal more damage or that his support also helps increase the game's duration. Similarly, when Kassadin is played with Jarvan IV on the same side, he usually scores many fewer killing sprees compared to when he plays alone. This is contrasting evidence that he is worse when playing alongside Jarvan IV.
Additionally, when Kassadin plays with Jarvan IV on the same team, he typically receives a little less damage than when he fights alone. Receiving not as much damage could mean that Jarvan IV does a decent job of covering Kassadin during teamfights.
There is no universally accepted best companion for Kassadin that will no matter what be his top teammate. Yet, Jarvan IV is a very typical teammate for Kassadin. By playing on the same team as Kassadin, he drops their win rate by -0.8% to 49.2%. This clearly indicates that there is a weak strategic relationship between Kassadin and Jarvan IV that allows them to perform worse together than without each other.
Jarvan IV has a much lower diffuclty than Kassadin. That means you don't need to be very careful when finding Jarvan IV teammates to play with, as they will have to have a much lower level of skill to be able to cooperate well with you.
Working together, Kassadin players should expect to observe an overall large increase in your team’s capability to soak up damage. Together, these champs will be a great protective duo.
In contrast, by aligning Kassadin and Jarvan IV together, you will not be providing your side a lot of crowd control. Plan to pick other champions on your team that offsets this relative gap in this pairing's capabilities.
Regardless of your Jarvan IV ally's ability, you should focus on maximizing your income, outlasting your enemies, and clearing objectives. If you heed this simple advice, you will do well, regardless.
To truly master Kassadin in order to work well with Jarvan IV during both the lane and mid / late game phases of League of Legends games, you should keep reading to master some more lessons on this champion pairing. If you pay attention to the build and tips displayed above, you will increase your win rate significantly.
The top items to build first in your Kassadin and Jarvan IV synergy build include Seraph's Embrace, Rabadon's Deathcap, and Malignance. When Kassadin incorporated at least these three finished items in his build, he performed much better as an ally of Jarvan IV than with many other common builds. In fact, Kassadin had an average winrate of 49.2% helping carry Jarvan IV with this build.
To have the greatest likelihood of crushing your oponents, you should equip the First Strike, Magical Footwear, Future's Market, Cosmic Insight, Sudden Impact, and Ultimate Hunter runes from the Inspiration and Domination rune sets. Of all the rune combinations players chose for Kassadin and Jarvan IV pairings, this order of runes yielded the top win rate. Notably, these runes averaged a 49.2% winrate overall.
By default, tips, statistics, and builds on how to team up Jarvan IV with Kassadin are shown for all ranked divisions combined. If you want to narrow the stats and builds to an individual skill level, you may use the selection menu located earlier on the page.