Domains are unique in every sense of the word. And quite frankly, no two persons can have the exact same domain. It's a sort of universal rule. Even if their characters and desires are exactly the same, as long as one has created a certain type of domain first, then the other won't be able to do the same. Even if they're similar, they'll never truly be the same.
Gideon didn't know why, the the instant he uttered those words, this information entered his mind. Maybe there was someone in the past who had a similar domain, or maybe he was the first to create this type of domain. Either way, he didn't know. What he did know though was that his domain, wasn't weak. And that was putting it very lightly.
The instant the words came out of his mouth, an invisible wave that travelled faster than Gideon had ever observed spread out from his body. And as it did, the two Domains the mages cast were destroyed. Their eyes widened as they coughed up blood from the backlash.