How did you do it?

After the main battle was finished and Liam started absorbing everything with his stone tablet, the rest of the activities did not take too long.

Another fifteen to twenty minutes later, the last of the vampires got mercilessly crushed by the white fox, and the battlefield was completely cleared out.

Liam did not wait until the last second as he was not completely sure whether the fairies would pull some sort of underhanded tricks or not. 

So a couple of minutes before the last vampire died, he had already packed up the stone tablet back into his spatial artifact. He also dismissed his soul minions around the same time, fully ready to exit the battleground arena.

There was another reason why he was rushing everything, and this was because of Jonathan's taunting words at the beginning of the battle. 

He had mentioned something about sending more vampires to the base and attacking them from both sides.