By d. emerson eddy — Since his surprise heel turn in the most recent volume of The Avengers, Namor has been a difficult character to pin down. This has been true of his motivations and actions lately through the stories in that series, as well as in the Defenders: The Best Defense crossover, and here in the new Invaders series, too. His erratic mood swings, as he went back and forth seemingly indiscriminately between hero and villain, were once explained by an “oxygen imbalance” in his blood, but we were told earlier in this series that this isn't the case now. With all that in mind, this issue begins to explain Namor's hidden history and how it might feed into why…