is the infinite challenge a garanteed drop from the questline?

[Dalapie]

really want it, its in black or crimson, but is it garanteed after the quest chain and how to do it:P? what quest to trigger to start the event.

[Cynabunny]

isn't that the outfit a rare drop from dreadtide arena?

[Cor]

14 minutes ago, Cynabunny said:

isn't that the outfit a rare drop from dreadtide arena?

^This, there is no quest for it.

[Inkswan]

It can drop but is not guaranteed to drop. I got crimson one on first try killing the guy at 42lvl when I was doing the quest but when my friend tried it few times at 45lvl he didn't see the costume at all. So it is purely rng like other drop costumes.