Iritsista Rainbow Astracite where to get???????

On the 2nd floor shop the Iritista Rainbow Astracite they be exchanged for some of the most powerful weapons in the game. Example Elder Rifle for 50 Rainbows.

My questions are:

  1. Where can you find Iritista Rainbow Astracite? what missions?

  2. Can you buy Iritista Rainbow Astracite in the personal shop?

  3. Can you get Iritista Rainbow Astracite them through trade with another player?

  1. They are a drop from the UQ Elder of the Unfathomable Abyss .

  2. No.

  3. No.

Thank You