Lead your enemy when targeting with Noxious Blast to ensure the hit.
Use Twin Fang on poisoned stationary targets like monsters and units stunned by her Petrifying Gaze for maximum damage.
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 shown here emphasize several significant Cassiopeia vs. Karthus counter stats that may help us distinguish the differences and similarities between the pair. Cassiopeia’s KDA ratio ([kills + assists] / deaths) of NaN is greater than Karthus’s KDA ratio of NaN, showing that Cassiopeia may be more central to her team's team fighting potential than Karthus..
Cassiopeia normally has a similar longest kill spree as her foe does. Commonly, she receives a similar amount of damage to Karthus. This often reflects differing health capacities, yet it can also hint that the champ with increased health has less agility and thus is not able to escape additional damage when engaged or poked.
Both League champions are great. Both have their pros and cons. In League's current meta, Cassiopeia usually wins when playing against Karthus, with a 54.4% win rate. Therefore, Cassiopeia makes a great counter to Karthus.
While Cassiopeia does have a much higher win rate than Karthus, when facing one another, Cassiopeia also has a much greater level of difficulty that makes her a more challenging champ to learn. You don't need to be too worried when picking Cassiopeia into Karthusas her relative depth means you may not be able to reach her full potential without a significant amount of practice beforehand.
Furthermore, Cassiopeia also has a good amount of CC and other utility, 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 is not a single best champion overall in League of Legends, in Cassiopeia vs Karthus matchups, Cassiopeia is the better champ with a noticably higher win rate, more champion depth, and a similar amount of utility to help out your allied champions during teamfights.
Cassiopeia is a great counter to Karthus. You will do well by focussing your actions on increasing your gold and cs and clearing objectives. If you can do that, you should do very well as Cassiopeia against Karthus.
If you would like to learn all of the intricacies of Cassiopeia in order to counter Karthus during both the early game and mid / late game phases of League of Legends, you should keep reading to gather a few extra lessons on this matchup. If you mind the build and suggestions displayed above, you will increase your win rate significantly and be that much closer to League of Legends pro players.
Cassiopeia often gets more CS relative to Karthus. Champions who typically don't earn many minion kills typically don't need much CS to be valuable teammates, such as support champions. These kinds of champions are capable of scaling well off of their abilities and first items alone. Yet, champions with large amounts of CS, such as hyper-carries, often have to have many items to be effective. In either situation, try to surpass the values displayed here to do well.
The most important items to prioritize in your Cassiopeia versus Karthus build include Seraph's Embrace, Rylai's Crystal Scepter, and Liandry's Torment. When Cassiopeia included at least these three pieces in her build, she did significantly better vs Karthus than with most other common item sets. In fact, Cassiopeia boasted an average win rate of 54.4% when playing against Karthus with these items in her kit.
To have the best chance of vanquishing Karthus as Cassiopeia, Cassiopeia players should equip the Conqueror, Presence of Mind, Legend: Tenacity, Last Stand, Manaflow Band, and Transcendence runes from the Precision and Sorcery rune sets. Out of all the rune combinations players picked for Cassiopeia vs Karthus counter picks, this composite of runes yielded the greatest win rate. Moreover, these runes averaged a 54.4% win rate overall.
By default, tips, statistics, and builds on how to beat Karthus as Cassiopeia are shown for all skill levels, merged. To scope the statistics and builds to a particular rank, you should use the selection menu at the top of this page.