[quote]Why didn't Frodo just fly those winged monsters all the way to Mt. Doom? [/quote] The eagles did not like the other creatures of middle earth, they only liked Gandalf because he saved the eagle lord's life. [quote]Why didn't somebody just use Avada Cadavra on Voldemort's snake? [/quote] Horcrux's can only be killed in specifically magical ways, such as basilisk venom or goblin weaponry, not something as basic as a spell.