Although he didn't know what was happening on the other side... Antlers realized the screams from "Mr. Thunder" could possibly attract the Giants.
So, his first reaction was to randomly seal three doors that he had never opened.
He didn't know where these doors specifically led to.
They had not yet found the kitchen or the banquet hall—the place where the "Magic Cauldron" was. Nor had they found the bedroom where the Giant couple rested. In order not to block the doors to the "Magic Cauldron," Antlers didn't seal any room doors.
But they had already identified more than one safe route.
Even if they were chased by a Giant, they had their own escape paths.
In such a situation, it would certainly be a good move to block any door they hadn't seen before.
He didn't know if he could block the Giants... but at least he could block the routes for other teams to rush here or the escape routes of Mr. Thunder and his team.
