Does this help (taken from https://plarium.com/forum/en/raid-shadow-legends/673_guides-and-tutorials/594614_basic-guide-artifacts-overview/ )? You want that place where it says "Primary Stat" to say "ATK (%)".

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@OP Missions like the one you speak of can be confusing to new players (which I was just like you at one time)

I will only say to you, READ the  mission requirements word for word and understand EVERY word. As it can be tricky at the best of times for  new  players to understand what they are requiring  of you

Having dane all the  missions and  got  my free Arbiter(love her) , now working  on the next free lego

I will say all missions are completable, but often misunderstood