I dare say those materials are probably tied to another dungeon that is yet to be released. Now whether that is another frontier dungeon or not though? Celestial makes me think of the Silent planet, but devs have hinted thats still some time away from release. So who knows really...

I think the recent "Shinobi" dungeon will become a permanent addition which will drop the awakening shards required for the Cosmic Shinobi (and possibly Musashi/Oni/regular Shinobi's etc) as well. Devs will remain quiet if that indeed is the case. They don't want to give too much away usually.

I guess they didn't think about those who managed to get the first Moonchild or first few Moonchild's in the first month of the current Season of Gauntlet too much. I guess its a nice problem to have at this stage though, just looking at those ATK and MAGIC stats, god damn.