On this page, you will find more information about the most common causes and most relevant solutions for the League of Legends error 'Unknown direct x error'. Do you need help straight away? Visit our support page.
The Riot Games documentation indicates that error code 'Unknown direct x error' is caused by the following problem: "This direct x error appears during graphical instabilities and prevents players from launching the League client.".
Do you think there is another cause for this error? Let others know in the comments.