Once he was done reminiscing about Aria's magic, Marcus turned to look at his prisoners one time to make sure they were all fully secured and incapacitated before taking off.
Now that his goal of getting rid of the Dungeon Marauders, who in actuality turned out to be soldiers from the empire on the continent to the east of Borealia, Marcus needed to transport them back to the capital and hand them over to the relative authorities.
There was no doubt this was going to cause another mess for the kingdom, but at least whatever had been happening here had been nipped in the bud by Marcus' fortunate arrival.
If he had not shown up in Lethallan when he did, it was likely that the activities of the empire's soldiers would have gone on for much longer without being discovered, and the people here would have bene whittled down and shipped over to be used as slaves.