the achievements give me a minus unfortunately I see that no one answered me 

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8.7 artifact challenge

u need 3 diffrent 2 pieace sets... For Example each char will need 2 pieaces from the 2 pieace HP set, 2 pieaces from the 2 pieace atk % set, and 2 pieaces from the 2 pieace of the Crit set   all which have to be 4Star or higher and lvled to 12

put on each champion 2 items of any set this time 3 on each hero .dossent matter if the sets are from 2 or 4 .Example 2 life should be 4 star lvl 12, 2offense 4 star lvl 12, 2 deffense 4star lvl 12...SImple

Thanks so much for the help, the key was the x3 sets, that should be 4* at level 12 or higher. I tried and tried, spending also alot of coins not getting it right. Thanks again, helps to google sometimes hey...