League of Legends Karthus players will find him to be a difficult champ to build out properly. You'll find that his build changes when he is up against either diversified or highly focused team comps, indicating you should not select the same Karthus build every single game of League of Legends
The most critical items to include in your champ's build include: Dolore di Liandry, Copricapo di Rabadon, and Bastone del Vuoto. Players who added these items in their builds had a significantly better winrate than players who tried for other builds for Karthus. Moreover, if you are fighting a mixed enemy team composition, you should really consider grabbing yourself the Ispirazione, and Dominazione runes. In recent games, he won the largest fraction of his games when equipped with these runes.
We established our Karthus build guidance by examining 33.687 recently ranked League of Legends games with him selected. We only advise the best winrate Karthus builds that have been used by ranked LoL players enough times for us to advise them. With so many rounds in our data, we are quite confident in our recommended builds.