Moalith gets rewarded in special events from time to time, so watch out for them. They get announced through the online-portal. There are also some special events where you can get Moalith as a challenge reward.
“Moaliths show up maybe, once a month I think? No need to worry, they’re quite regular, and they’re not going to stop coming. Although you’d better make sure your ticket cap is at least 30 by then, because that’s how much you’ll need in order to get it.”
So there are no set dates when they’ll come but they’ll come eventually.
Moaliths come from an event that happens roughly once every month ish, as boilertribe said the last one was a couple weeks ago so you shouldn’t have to wait too long for the next one relatively speaking.
They’ve also been available as high level rewards for some events in the past, so keep an eye on the rewards tables for one popping up.