These 'Gluttons' became massive in size, often reaching heights of over ten meters. They were simply 'Giants' in a sense and ate whatever came in their way. They were quite resistant to damage, both physical and magical.
Only light magic and holy magic could harm them and as for the physical damage, an entire army would be needed to kill just one of them. But that was not the problem, as sending an army to fight a glutton was often a great mistake.
While an army had the advantage of numbers, that didn't really work well against a Glutton. An individual soldier of the army might not even be as strong as an average Lost, not to mention a Glutton.
This ended up with the gluttons eating the army soldiers, while the rest exhausted their stamina. First of all, the damage done was quite less and even the little damage that was done was healed by the Glutton.