v. 99 - Chaos: Age of Artisans Update Notes

Ah dude.
Nothing else is confirmed to drop it. ;/
Read: Unavailable forever.

"Forever" is such a long time.
Either they'll use it for another event, or it'll come from gacha, or time will pass and it will be superseded by some other, much better, Ring or Set.

Deciding that a whole update, with an entire crafting system and a bewildering array of new and amazing equips and potions, is utterly worthless because you can't get the 10-attack ring you were counting on, is ... well ... it reminds me of my little nephew declaring that the whole day at the amusement park is fail, just because the cotton-candy cart was nowhere to be found the park's "flagship ride" is closed for repairs.