Does anyone know how much damage per attack he does?
In the original CoC, there was no contest. It wasn't "can we beat him?" It was "how many can he eat before we escape?"
Big C. swallowed 1d4 people per round. No save, 100% chance of doing so.
His sight generated 1d10/1d100 (save/no save) insanity points just seeing him, so if you didn't have a high SAN, or if you failed the roll, you were screwed. Remember, 20% Sanity loss, and you were gibbering on the floor - long enough for you to be the next meal.
If they can recapture that, then I'm happy.