This was so obvious when I realized it, but I think most people miss it, because we鈥檙e so desensitized by D&D-style magic with immediate, visibly, flashy effects, rather than more subtle and invisible forces of magic. When Gollum attacks Frodo on the slopes of Mount Doom, Frodo has the chance to kill him, but he doesn鈥檛. Instead, he says:
Frodo: Go! And if you ever lay hands on me again, you yourself shall be cast into the Fire!
Frodo鈥檚 not just talking shit here. He is literally, magically laying a curse. He鈥檚 holding the One Ring in his hands as he says it; even Sam, with no magic powers of his own, can sense that some powerful mojo is being laid down. Frodo put a curse on Gollum: if you try to take the Ring again, you鈥檒l be cast into the Fire.
Five pages later, Gollum tries to take the Ring again. And that鈥檚 exactly what happens. Frodo鈥檚 geas takes effect and Gollum eats lava.
"Don't look at it!" Her commander yelled. "Close your eyes!"
It's too bad she had already locked eyes with the creature. She watched the serpent's head as it arched down to stare through her, seemingly straight to her soul.