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 underscore several critical Rell vs. Karthus counter stats that can help you grasp the distinctions between this pair of champions. For instance, Rell’s KDA ratio ([kills + assists] / deaths) of NaN is more than Karthus’s KDA ratio of NaN, highlighting that Rell may be more central to her team's team fighting effectiveness than Karthus. This observation is largely fueled by the differences in assists.
Rell typically has a significantly smaller longest kill spree than her opponent does. On average, she receives less damage than Karthus. This typically indicates differing health capacities, but it can also indicate that the champion with increased HP has less mobility and thus is not able to kite away from further damage when poked or engaged.
Both League of Legends champions are great. Both have their strengths, weaknesses, and counters. In the game's current meta, Rell usually wins when facing off against Karthus, with a 51.4% win rate. Therefore, Rell makes a good counter to Karthus.
While Rell does have a higher win rate compared to Karthus, when on opposite teams, Rell also has a much lower learning curve that makes her a less difficult champ to pick up and master. You should be careful when picking Rell into Karthus.
Furthermore, Rell also has a very large amount of utility and CC, a similar amount to Karthus. This often makes her just as valuable during team fights, especially when fighting champions with a ton of burst damage.
While there isn't a single best champion overall in League of Legends, in Rell vs Karthus matchups, Rell is the better champ with a higher win rate, less champion complexity, and a similar amount of utility to help out your teammates during team fights.
Rell is a decent counter for Karthus. You will do well by focussing your actions on maximizing your gold income and taking out objectives. If you can do that, you should hold your own as Rell against Karthus.
If you would like to truly master Rell to counter Karthus during both the early game 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 pay attention to the build and suggestions displayed above, you will grow your win rate significantly and be that much closer to League of Legends pro players.
Rell most often accumulates a lot less CS compared to Karthus. Champions who on average don't earn much CS often don't need much CS to be effective, such as sup champs. These kinds of champions are able to scale properly off of their abilities and first items alone. Yet, champs with large amounts of CS, such as hyper-carries, often have to have a lot of items to be effective. In either situation, try to surpass the values reported on this page to do well.
The best items to use in your Rell versus Karthus build include Trailblazer, Zeke's Convergence, and Celestial Opposition. When Rell incorporated at least these three items in her build, she did much better vs Karthus than with many other commonly used counter builds. In fact, Rell boasted an average winrate of 51.4% when playing against Karthus with this build.
To have the best chance of vanquishing Karthus as Rell, you should use the Glacial Augment, Hextech Flashtraption, Biscuit Delivery, Cosmic Insight, Bone Plating, and Unflinching runes from the Inspiration and Resolve rune sets. Of all the rune combinations players picked for Rell vs Karthus clashes, this combination of runes resulted in the greatest win rate. In fact, these runes provided a 51.4% win rate overall.
If you would like to see Rell versus Karthus tips and counter stats for a a specific division rank, feel free to select one from the selection menu shown above. If viewing for the first time, the statistics and guides given are computed using all games played with both champions.