Giants were quickly eaten by a cabal of unicorns, harpies, basilisks, griffins, sphinxes, birdmen, and other all-too-real monstrosities. I have personally authenticated every single observation made by Sir John Mandeville and Isidros of Seville, and I know that all these creatures once existed, and continue to exist, in the far reaches of the Canadian Arctic and the Hart Senate Office Building. Also, you should be wary of sailing over the horizon, lest terrible sea monsters get you.