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.
Command: Protect can be used on yourself to return the Ball back to you quickly. Combine this with Command: Attack for a quick harassment.
Command: Dissonance is a very powerful escape tool if Orianna has the Ball. The combination of speed and leaving a slowing obstacle can be quite powerful.
Command: Shockwave can be used to drag enemies towards you or away from you if you position the Ball properly.
The Karthus Orianna synergy stats shown here demonstrate the areas of his gameplay that do better (or worse) when paired with Orianna, 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 Orianna. His KDA went down from NaN to NaN. This negative change shows that Orianna helps Karthus perform poorer in ranked League of Legends matches. Yet, the small difference proves that this performance change is not very impactful.
When Karthus tries to synergize with Orianna, he sees a small decrease in his complete damage dealt. This change may demonstrate that Orianna doesn't help cover for him to deal more damage or that her support also helps increase the match's duration. Similarly, when Karthus is played with Orianna on the same team, he usually scores many fewer killing sprees compared to when he plays on his own. This is contrasting evidence that he is worse when playing with Orianna.
Additionally, when Karthus plays with Orianna on the same side, he often receives a little more damage than when he plays alone. Taking more damage could mean that Orianna does a poor job of covering Karthus during team fights.
There is no universally accepted best champion pairing for Karthus that will 100% of the time be his #1 ally. However, overall, Orianna is a very bad companion for Karthus. By locking into the same side as Karthus, she drops their win rate by -9.3% to 38.0%. This shows that there is a terrible synergy between Karthus and Orianna that results in them performing worse together than without each other.
Orianna has a lower difficulty than Karthus. That means you don't need to be careful when enlisting Orianna teammates to play with, as they will require a lower level of skill to fight well with you.
Playing together, Karthus players will likely observe an overall large increase in your team’s capability to to do a lot of AP damage. Combined, these champs are able to dish out a surprising amount of magic type damage.
Conversely, by pairing Karthus and Orianna together, you may not be granting your other allies a great deal of protection for burst damage. Make sure to bring other champs on your team that neutralizes this gap in their kit.
Regardless of the ability of your Orianna teammate, you should focus on maximizing your income, warding to avoid ambushes, and taking down objectives. If you do this, you will do well anyway.
To truly master Karthus in order to work well with Orianna during both the laning and mid / late game phases of League of Legends rounds, you should keep reading to master a few extra tricks and insights into this champion pairing. If you pay attention to the build and stats shown here, you will grow your win rate by a lot.
The best items to have in your Karthus and Orianna synergy build include Rabadon's Deathcap, Malignance, and Liandry's Torment. When Karthus bought at least these three finished items in his build, he did significantly better when fighting alongside Orianna than with most other typical builds. In fact, Karthus had an average winrate of 38.0% when synergizing his build and playstyle to Orianna with this build.
To have the highest likelihood of annihilating your oponents, you 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 combinations players chose for this team composition, this composite of runes yielded the highest win rate. In fact, these runes averaged a 38.0% winrate overall.
By default, tips, stats, and builds on how to pair Orianna with Karthus are given for all ranked divisions. If you want to narrow the statistics and builds to a particular rank, you can use the selection menu earlier in the counter matchup guide.