Training [1]
There was no need to overexplain what happened then.
Damien had already done something like this a few times.
The young Liqua Clan dragons had been sent to investigate what everyone thought was a treasure. This excursion was a learning experience for them. They weren't equipped to deal with someone of Damien's caliber in the slightest.
As such, they couldn't put up a shred of resistance as he toyed with their existences. No, they didn't even realize they were being manipulated.
The five of them fell unconscious. Their memories changed drastically as an experience they never had became real, and their environment followed suit. A dungeon that "didn't exist" was born in the empty plain, entrenched in the ground and overgrown as if it had been there since the beginning of time.