Cloud 9 Is the first NA to ever beat a Korean team during the worlds quaterfinals. Yes NA teams have beaten Korean teams during the group stage, but an NA team has never knocked out a Korean team in the quaterfinals until now. The links below are all worlds matches and you can see for yourself that NA has never beaten a Korean team in the quaterfinals.
(I mean no hate/BM when I say this. I am just happy that Cloud 9 has finally done it. Please don't misunderstand what I mean)