There is a short calendar on Plarium Play for events.  Generally we won't ever know more than a few days ahead of time.

Thank you. Was hoping it would be a week or something. Oh well. 

During fusions, you'll see the list here. And those happen every month and a half, roughly.

I am new to the game and I hope someone can answer my question!   When you sacrifice and champion do you get a higher upgrade in level if you leave the artifacts with the champion.   Seems like a lot of time to remove artifacts and cost in silver coins.   

So, it's not that I feel stupid; it might just be basic noob misunderstanding, but in Arbiter Missions the Campaign Missions seems stuck at 18/21. What am I not getting? Please and thank you.

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To get 3* on a campaign missions, you have to do it with only 2 champs, they both have to be alive at the end AND you have to complete it in under 10 minutes.

That last part is not well explained at all and a ton of players miss it.

No, if you leave artifacts on a champ being sacrificed, they're just destroyed and lost.

Generally, players don't put any gear on champs that will just be used as sacrifices, often referred to as "chickens", but it's a lot harder to manage that when you're still pretty early in the game and don't yet have a good solid team to farm most of the content.