From Dragon Quest Wiki

Darkonium starts out as dark matter that gets captured in the sun. Any of it that escapes the sun crystallizes into darkonium.

What is found of it in the Dragon Quest universe is treasured as rare and extremely powerful.


Dragon Quest Monsters: Joker[edit]

Dr. Snap uses Darkonium to change a Wulfspade ace into an Ace of spades.

Dragon Quest Monsters: Joker 3[edit]

Darkonium returns as a major plot element, where exposure to concentrated darkonium turns normal monsters into BREAK Monsters.