Aang stood on top of the volcano without moving, his eyes closed. Even though Sokka knew he was immensely powerful, capable of wielding all four elements (well, only three so far), and stronger than all the others, he looked small and defenseless.
Remembering their encounter a few days ago with that crazy man who'd tried to explode them with his mind, Sokka glanced behind him, his hand flying to the hilt of his new sword. No one was going to sneak up on them this time.
And no one was going to hurt Aang. Sokka wasn't going to allow it.