for those challenges, you need to use artifacts from matching sets. if the champion meets the requirements, you should see three little symbols like the ones pictured below that indicate the set bonuses the champ is getting.

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Thanks, I'm going to try and I'll get back to you !

My question would be why here the 3rd badge from the avenging artifacts doesn't count ?

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iirc that one is something like equip two champions with 3 5 or 6* sets? so that will have to be 3 different two piece sets. you only have two in this picture.

To clarify: avenging is a 4 piece set, not a 2-piece set

some artifact sets, including avenging, require four pieces to get the bonus rather than just two. because of that, you won't be able to use artifacts from any of them to complete these missions. 

if you look in your artifact storage, you can see the number of pieces a set requires written in parentheses after the set name.

Omg I never knew what the numbers meant 🥲 

I understand now thank you so so