If it was just to allow them to travel towards a certain area, then it wouldn't be a problem. Yet they had to fight, and that was a variable he couldn't predict.
Giving them a day? He was thinking about a week! He decided to go out there and help, trying to buy enough time for them to make more potions.
William didn't want to just let his small army use these potions, but all the entrapped masters in that valley. According to Sloth, there were hundreds of thousands entrapped there, with a fighting force equal to a hundred thousand and a half.
Thanks to such a large number, they managed to survive against the monsters, dark masters, and the toxin. He knew trying to save the day, win the battle solo was impossible. Yet trying to create trouble for the enemies and attract their attention wasn't that hard actually.
