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.
Fizz's spells scale off Ability Power - consider getting items like Zhonya's Hourglass or Banshee's Veil against teams that have high burst threat - and items like Lich Bane or Rabadon's Deathcap if you think you can survive without the Health.
Since Fizz can move through units, find opportunities in lane to walk through minions and apply Seastone Trident's passive - following it up with the ability's active attack after a few seconds.
Fizz's ultimate ability, Chum the Waters, can be aimed at an enemy or towards the area where you think they'll be going.
The Karthus Fizz synergy stats shown here demonstrate the areas of his gameplay that do better (or worse) when paired with Fizz, compared to his overall stats. Significant differences are areas of focus that highlight how his gameplay changes when paired with this other champion.
Overall, Karthus sees a very large drop in his KDA (ratio of kills and assists to deaths) when paired with Fizz. His KDA went down from NaN to NaN. This drop shows that Fizz helps Karthus perform not as well in ranked League of Legends matches. Yet, the small difference demonstrates that this performance change is not very impactful.
When Karthus is paired with Fizz, he sees a little decrease in his full damage dealt. This change could signal that Fizz does not support by providing protection for him to deal more damage or that his presence also helps increase the round's duration. Similarly, when Karthus is played alongside Fizz on the same side, he usually scores many fewer killing sprees than when he plays on his own. This is contrasting evidence that he is worse when playing alongside Fizz.
Moreover, when Karthus plays with Fizz on the same team, he often takes a little more damage than when he fights alone. Getting dealt more damage could mean that Fizz does a poor job of protecting Karthus in team fights.
There is no perfect companion for Karthus that will always be his #1 ally. However, Fizz is a great teammate for Karthus. By being on the same side as Karthus, he raises their win rate by 4.0% to 51.3%. This shows that there is a strong synergy between Karthus and Fizz that allows them to perform better together than without each other.
Fizz has a lower difficulty than Karthus. That means you don't need to be very careful when lining up Fizz comrades to fight alongside, as they will have to have a lower level of skill to play well with you.
When playing on the same side, you should witness an overall large increase in your team’s capacity to deal magic damage. Combined, these champs are able to dish out a surprising amount of magic type damage.
Conversely, by pairing Karthus and Fizz together, you will not be giving your other teammates very much utility. Make sure to pick other champions on your team that neutralizes this disparity in this pairing's abilities.
Regardless of your Fizz ally's ability, you should focus on increasing your income, warding to avoid ambushes, and taking down objectives. If you do this, you will do well, regardless.
If you would like to truly master Karthus to synergize with Fizz during both the laning and mid / late game phases of League of Legends rounds, you should continue reading to pick up some more tips and tricks for this champion pairing. If you mind the build and stats displayed here, you will increase your win rate significantly.
The most crucial finished items to prioritize in your Karthus and Fizz synergy build include Rabadon's Deathcap, Void Staff, and Liandry's Torment. When Karthus used at least these three great items in his build, he did much better when fighting alongside Fizz than with many other common builds. In fact, Karthus had an average win rate of 51.3% helping carry Fizz with this build.
To have the highest chance of vanquishing your oponents, you should equip the First Strike, Magical Footwear, Future's Market, Cosmic Insight, Eyeball Collection, and Ultimate Hunter runes from the Inspiration and Domination rune sets. Of all the rune sets players used for Karthus and Fizz pairings, this order of runes resulted in the best win rate. In fact, these runes provided a 51.3% winrate overall.
If you would like to view Karthus and Fizz collaboration tips and builds for a a distinct player tier, please select one from the selection menu shown above. If viewing for the first time, the stats and guides given are calculated using every match with data with these champions.