Celestial world boss question

[melodramocracy]

To trigger the possibility of acquiring loot from them, do you have to defeat all 4? Or is any one of them all that's required? And is this a weekly reset like other world bosses?

[Pebrocks The Warlock]

Defeat one of them and you get loot. You can only get one loot weekly, and can't get more by defeating the others on the same week.

[Rokom]

To trigger the possibility of acquiring loot from them, do you have to defeat all 4? Or is any one of them all that's required? And is this a weekly reset like other world bosses?

Just one and it's weekly. The only reasons for taking down all four are for an achievement and for the legendary cloak chain, but doing them all in the same week isn't required for either of those.