Lay Waste is very strong at farming minions and harassing enemy champions.
Ask your allies to help point out when you should use Requiem to get kills in different lanes.
Jax benefits greatly from items that have both Ability Power and Attack Damage such as Guinsoo's Rageblade and Hextech Gunblade.
Jax can Leap Strike to friendly units, including wards. You can use them to plan your escape.
The Karthus Jax synergy stats shown here demonstrate the areas of his gameplay that do better (or worse) when paired with Jax, compared to his overall stats. Significant differences are areas of focus that highlight how his gameplay changes when paired with this other champion.
Overall, Karthus sees a very large drop in his KDA (ratio of kills and assists to deaths) when paired with Jax. His KDA decreased from NaN to NaN. This fall shows that Jax helps Karthus perform not as well in ranked League games. Yet, the small difference shows that this performance change is only marginal.
When Karthus is an ally to Jax, he observes a barely noticable drop in his total damage output. This may demonstrate that Jax does not provide protection for him to dish out more damage or that his presence also helps extend the round's duration. Similarly, when Karthus is played together with Jax on the same team, he usually scores many fewer killing sprees than when he plays on his own. This is contrasting evidence that he is worse when playing alongside Jax.
Additionally, when Karthus plays with Jax on the same side, he often receives a little less damage than when he plays alone. Getting dealt not as much damage could mean that Jax does a decent job of covering Karthus in teamfights.
There is no top synergy for Karthus that will 100% of the time be his #1 ally. Yet, overall, Jax is a pretty good teammate for Karthus. By playing on the same team as Karthus, he improves their win rate by 1.9% to 49.2%. This shows that there is a good bond between Karthus and Jax that results in them performing at the top of their game together than alone.
Jax has a lower difficulty than Karthus. That means Karthus players don't need to be very careful when finding Jax comrades to fight alongside, as they will need a relatively low level of skill to play well with you.
When playing cooperatively, Karthus players should expect to observe an overall large increase in your team’s capability to to do a lot of AP damage. When paired, these champs are able to dish out a surprising amount of magic type damage.
Conversely, by grouping Karthus and Jax together, you probably will not be giving your other teammates a lot of engage potential. Make sure to have other champs on your team that fills this gap in this pairing's kit.
Regardless of your Jax ally's ability, you need to focus on increasing your gold income, warding to avoid ambushes, and taking down objectives. If you heed this simple advice, you will do well, regardless.
If you would like to truly master Karthus in order to synergize with Jax during both the lane and mid / late game phases of LoL, you should keep reading to pick up some more tips and tricks for this champion pairing. If you listen to the build and tips shown above, you should grow your win rate significantly.
The ideal finished items to build first in your Karthus and Jax synergy build include Malignance, Zhonya's Hourglass, and Liandry's Torment. When Karthus included at least these three pieces in his build, he did significantly better as an ally of Jax than with many other common builds. In fact, Karthus had an average winrate of 49.2% when playing alongside Jax with these items in his kit.
To have the highest chance of crushing your oponents, Karthus players should take the Dark Harvest, Cheap Shot, Eyeball Collection, Ultimate Hunter, Presence of Mind, and Last Stand runes from the Domination and Precision rune sets. Of all the rune sets players used for Karthus and Jax pairings, this order of runes yielded the top win rate. In fact, these runes averaged a 49.2% win rate overall.
If you want to see Karthus and Jax cooperations tips and stats for a a distinct division rank, feel free to select one from the selection menu above. At first, the stats and strategies shown are calculated using all games finished with both champs.