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.
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.
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 stats shown on this page feature some strategic Sivir vs. Karthus counter statistics that may help us realize the differences and similarities between this set of champions. For instance, Sivir’s KDA ratio ([kills + assists] / deaths) of NaN is greater than Karthus’s ratio of NaN, showing that Sivir may be more central to her team's team fighting capacity than Karthus..
Sivir normally has a similar longest kill spree as her enemy does. Commonly, she receives less damage than Karthus. This typically indicates different amounts of tankyness, yet it can also imply that the one champ has less agility and thus is not able to flee from additional damage when poked or engaged.
Both LoL champions are great. Both champs have their pros and cons. In League's current meta, Sivir usually wins when playing against Karthus, with a 54.5% win rate. Therefore, Sivir makes a great counter for Karthus.
While Sivir does have a much higher winrate compared to Karthus, when on opposite teams, Sivir also has a lower level of difficulty that makes her a less complex champion to develop with. You don't need to be too worried when picking Sivir into Karthus.
Furthermore, Sivir also has almost no amount of utility and CC, a similar amount to Karthus. This makes her just as valuable during team fights, especially when fighting champions with a lot of burst damage.
While there isn't a single best champion for every situation in League of Legends, in Sivir vs Karthus matchups, Sivir is the better champ with a noticably higher win rate, less champion complexity, and a similar amount of utility to help out your teammates during teamfights.
Sivir is a great counter to Karthus. Make sure you focus your gameplay on keeping up your CS and destroying objectives. If you are able to do that, you should hold your own as Sivir against Karthus.
To learn all of the intricacies of Sivir to counter Karthus during both the laning and mid / late game phases of League of Legends, you should continue reading to gather a few extra lessons on this matchup. If you mind the build and stats shown here, you will grow your win rate significantly and be closer to League of Legends pro players.
Sivir on average accumulates more CS as Karthus. Champs who typically don't get much CS usualy don't require much CS to be valuable teammates, such as sup champs. They are capable of scaling properly off of their abilities and first items alone. Yet, champions with a lot of CS, such as hyper-carries, usually need several high cost items to be effective. In either situation, try to surpass the values reported on this page to do well.
The best items to have in your Sivir versus Karthus build consist of Kraken Slayer, Infinity Edge, and Bloodthirster. When Sivir incorporated at least these three pieces in her build, she performed much better when fighting Karthus than with most other typical counter builds. In fact, Sivir boasted an average winrate of 54.5% when playing against Karthus with this counter build.
To have the best chance of beating Karthus as Sivir, Sivir players should take the Lethal Tempo, Presence of Mind, Legend: Bloodline, Cut Down, Magical Footwear, and Biscuit Delivery runes from the Precision and Inspiration rune sets. Out of all the rune combinations players picked for Sivir vs Karthus LoL games, this composite of runes yielded the highest win rate. In fact, these runes provided a 54.5% win rate overall.
By default, tips, statistics, and builds on how to beat Karthus as Sivir are displayed for all skill levels, merged. To narrow the stats and builds to a specific rank, you can use the selection menu located at the top of this page.