So I was thinking... Why do we take it as truth that the fire titan was killed? If the Ice Titan was broken in 12 pieces and survived as such, why the heck couldn't the Fire Titan immortal its way through a giant sword through the chest? Magic? Well, I would think magic is why it didn't collapse under its own weight, so it should have plenty to survive somehow. What are the odds our continent simply had the luck of 0 fire titan presence, while El had some which has steadily grown to power? Knowledge of something along these lines would certainly explain Lanostre's willingness to surrender to Varya - to strengthen Ice itself.