Dual?

"So as to match our slogan, I present you our last item for today's auction…"

"The Unique 'Omni Crystal' Collection!"

"Hmmm?"

"What's that supposed to be?"

"Is it a collection of elemental crystals…?"

"How long has it been since elemental crystals have been included in this auction…?"

"Well, it's usually only grade 3 elemental crystals and above that qualify to appear in this auction, but I wonder of which element would these crystals be…"

"The name seems to hint at something…"

The auctioneer didn't reveal the item from the very beginning, seemingly leaving the participants a chance to guess and get more excited to know what was this collection supposed to hold…

"Could it be…?"

Still, he didn't wait to long before he revealed the veil off the collection, revealing the whole collection of 111 elemental crystals put in a unique way to show their allure, while emphasising the main 10 grade 2 crystals.