Sivir's Boomerang Blade returns to her after reaching the max range, so you can shift position to hit enemies who would otherwise have evaded it.
Try saving Spell Shield for enemy abilities that can disable you such as stuns and roots.
Ricochet resets Sivir's basic attack timer on activation, so activating this immediately after landing a normal basic attack will maximize damage output.
Karthus can cast spells for a short duration after he is killed. Move away from his corpse to be safe.
Make sure you always have enough health to survive Requiem, even if you have to go back to the base more frequently to heal.
The stat comparisons provided here clarify several significant Sivir versus Karthus matchup statistics that may help you explain the differences and similarities between the pair. As an example, Sivir’s KDA ratio ([kills + assists] / deaths) of NaN is greater than Karthus’s KDA ratio of NaN, highlighting that Sivir may be more central to her team's team fighting effectiveness than Karthus..
Sivir often has a slightly smaller longest kill spree than her enemy does. Commonly, she receives less damage than Karthus. This is usually reflective of differing health capacities, yet it can also indicate that the one champ has less mobility and thus is not able to flee from additional harm when poked or engaged.
Both League champions are great champions. Both champs have their pros and cons. In League's current meta, Sivir usually fairs equally well when taking on Karthus, with a 49.0% win rate. Thus, Sivir makes an ok counter for Karthus.
While Sivir does have a lower winrate than Karthus, when on opposite teams, Sivir also has a lower level of difficulty that makes her a less time consuming champion to pick up and master. You still need to be cautious when picking Sivir into Karthus.
Moreover, Sivir also has almost no amount of CC and other utility, a similar amount to Karthus. This often makes her just as valuable during team fights, especially when facing champions with a lot of burst damage.
While there is not a single best champion in League of Legends, in Sivir vs Karthus matchups, Karthus is the better champ with a similar win rate, less champion complexity, and a similar amount of utility to help out your allies during late stage team fights.
Sivir is a somewhat poor counter for Karthus. Focus your actions on maximizing your CS and taking out objectives. If you can do that, you should hold your own as Sivir against Karthus.
To learn all of the intricacies of Sivir in order to counter Karthus during both the laning and mid / late game phases of League of Legends, you should keep reading to pick up a few extra tips and tricks for this matchup. If you listen to the build and stats displayed here, you should increase your win rate significantly and be closer to League of Legends pro players.
Sivir typically picks up more CS as Karthus. Champions who on average don't earn many minion kills often don't require much CS to be effective, such as support champions. They are capable of scaling properly off of their skills, stats, and first items alone. Yet, champs with large amounts of CS, such as hyper-carries, typically require many items to be effective. In either situation, try to surpass the numbers shown on this page to do well.
The top items to prioritize in your Sivir versus Karthus build include Bloodthirster, Kraken Slayer, and Navori Quickblades. When Sivir used at least these three pieces in her build, she did significantly better against Karthus than with most other common builds. In fact, Sivir had an average winrate of 49.0% when playing against Karthus with these items in her kit.
To have the greatest likelihood of vanquishing Karthus as Sivir, Sivir players should equip the Lethal Tempo, Presence of Mind, Legend: Bloodline, Coup de Grace, Biscuit Delivery, and Magical Footwear runes from the Precision and Inspiration rune sets. Of all the rune builds that we analyzed for Sivir vs Karthus battles, this set of runes yielded the highest win rate. Moreover, these runes provided a 49.0% win rate overall.
If you want to view Sivir x Karthus tips and builds for a an individual skill level, feel free to choose one from the selection menu displayed above. At first, the stats and strategies shown are computed using every round played with both champs.