Roar of the Slayer is a great setup ability to land a very powerful Decimating Smash.
The Soul Furnace buff displays how much shield strength is remaining, use this information to time its explosion perfectly.
You only have very slight turning ability during Unstoppable Onslaught, so make sure to use it in straight paths.
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.
The Sion Karthus synergy stats shown here demonstrate the areas of his gameplay that do better (or worse) when paired with Karthus, compared to his overall stats. Significant differences are areas of focus that highlight how his gameplay changes when paired with this other champion.
Overall, Sion sees a very large drop in his KDA (ratio of kills and assists to deaths) when paired with Karthus. His KDA fell from NaN to NaN. This fall shows that Karthus helps Sion perform worse in competitive League of Legends rounds. Yet, the small difference demonstrates that this performance change is not very impactful.
When Sion is an ally to Karthus, he gets a little increase in his total damage dealt. This could indicate that Karthus provides protection for him to dish out more damage or that his allyship also helps increase the round's duration. Similarly, when Sion is played together with Karthus on the same team, he usually scores many fewer killing sprees compared to when he plays alone. This is contrasting evidence that he is worse when playing alongside Karthus.
Additionally, when Sion plays with Karthus on the same side, he typically takes more damage than when he plays alone. Taking more damage could indicate that Karthus does a poor job of covering Sion in team fights.
There is no top champion pairing for Sion that will no matter what be his top synergy. Yet, Karthus is a very bad companion for Sion. By playing on the same team as Sion, he drops their win rate by -3.3% to 46.9%. This demonstrates that there is a very bad strategic relationship between Sion and Karthus that results in them performing worse together than alone.
Karthus has a greater difficulty than Sion. That means Sion players should be cautious when lining up Karthus comrades to go into battle on the same side as, as they will have to have a greater level of skill to fight well with you.
When playing cooperatively, Sion players will likely observe an overall large increase in your team’s capability to deal magical damage. Combined, these champs can blast through enemies with magic damage.
Conversely, by aligning Sion and Karthus together, you will not be providing your other teammates much AD. Make sure to bring other champs on your team that helps cover this hole in this pairing's capabilities.
Regardless of your Karthus ally's ability, you should focus on maximizing your gold income, outlasting your enemies, and clearing objectives. If you follow these simple suggestions, you will do well anyway.
To truly master Sion in order to work well with Karthus during both the laning and mid / late game phases of LoL matches, you should continue reading to gather a few extra tricks and insights into this champion pairing. If you pay attention to the build and tips presented above, you will grow your win rate significantly.
The most important finished items to have in your Sion and Karthus synergy build include Unending Despair, Thornmail, and Hollow Radiance. When Sion bought at least these three items in his build, he did significantly better when paired up with Karthus than with many other typical item sets. In fact, Sion had an average win rate of 46.9% when playing alongside Karthus with these items in his kit.
To have the highest chance of crushing your oponents, you should take the Grasp of the Undying, Demolish, Conditioning, Overgrowth, Approach Velocity, and Minion Dematerializer runes from the Resolve and Inspiration rune sets. Out of all the rune combinations players used for Sion and Karthus pairings, this blending of runes resulted in the greatest win rate. In fact, these runes provided a 46.9% winrate overall.
By default, tips, stats, and builds on how to pair Karthus with Sion are shown for all ranked divisions combined. If you want to scope the stats and builds to an individual rank, you can use the selection menu located above.