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.
Defiant Dance is not interrupted by crowd control, try timing it for incoming disables.
Flawless Duet does not have a maximum travel distance, try using it in creative ways.
Use Bladesurge to cover great distances by targeting low life minions on your way to champion targets.
The Karthus Irelia synergy stats shown here demonstrate the areas of his gameplay that do better (or worse) when paired with Irelia, 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 Irelia. His KDA decreased from NaN to NaN. This drop shows that Irelia helps Karthus perform poorer in competitive League of Legends games. Yet, the small difference indicates that this performance change is only marginal.
When Karthus plays on the same team as Irelia, he gets a little decrease in his total damage output. This change could indicate that Irelia does not support by providing protection for him to dish out more damage or that her presence also helps extend the round's duration. Similarly, when Karthus is played together with Irelia on the same team, he usually scores many fewer killing sprees than when he plays alone. This is contrasting evidence that he is worse when playing alongside Irelia.
Additionally, when Karthus plays with Irelia on the same team, he typically takes a little less damage than when he plays alone. Receiving not as much damage could indicate that Irelia does a decent job of covering Karthus during teamfights.
There is no one best synergy for Karthus that will always be his #1 ally. Yet, overall, Irelia is a good companion for Karthus. By being on the same side as Karthus, she increases their win rate by 1.7% to 49.0%. This signals that there is a good synergy between Karthus and Irelia that results in them performing at the top of their game together than without each other.
Irelia has a lower difficulty than Karthus. That means you don't need to be cautious when lining up Irelia teammates to fight alongside, as they will have to have a lower level of skill to be able to do well with you.
Playing alongside, you should see an overall large increase in your team’s capability to deal magic damage. Together, these champs can blast through enemies with magic damage.
In contrast, by bringing Karthus and Irelia together, you will not be giving your side enough engage potential. Plan to include other champs on your team that nullifies this relative disparity in their kit.
Regardless of your Irelia ally's ability, you need to focus on increasing your gold income, outlasting your enemies, and clearing objectives. If you follow these simple suggestions, you will do well, regardless.
To truly master Karthus to pair well with Irelia during both the early game and mid / late game phases of League of Legends rounds, you should keep reading to gather some more lessons on this champion pairing. If you pay attention to the build and suggestions displayed above, you will increase your win rate by a lot.
The top finished items to get in your Karthus and Irelia synergy build include Malignance, Shadowflame, and Stormsurge. When Karthus included at least these three items in his build, he did significantly better when paired up with Irelia than with most other typical builds. In fact, Karthus had an average win rate of 49.0% when playing alongside Irelia with these items in his kit.
To have the highest chance of defeating your oponents, you should use 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 builds players chose for this champion pairing, this mixture of runes yielded the best win rate. Notably, these runes provided a 49.0% win rate overall.
If you want to see Karthus with Irelia collaboration tips and builds for a an individual player tier, feel free to choose one from the selection menu above. If viewing for the first time, the stats and build suggestions given are computed using all matches run with these champions.