BURN IT ALL

Promethium was only discovered in the 1940s, a whole century after most of the other lanthanides. Its complete radioactivity is a curious product of several nuclear phenomena: the Oddo–Harkins rule, liquid drop nuclei (which, together with relativistic effects, explains the vast majority of heavier elements) and so on. Mendeleev did not anticipate an actinide series, that being created by Seaborg et al. with the first elements beyond plutonium, but as we’ve seen after 70 years he wasn’t that far off with the lanthanides only.

Luminous paint? Not surprised. That’s the only use of promethium I know of off the top of my head. Though I’ve heard tritium is safer in that application. As for samarium (The next lanthanide), I’m aware it’s used for magnets, like neodymium.

Gee, Sunset, you’re putting that fire awfully close to your-  
 
…too late.

@Ichijoe  
Is that seriously what Rand went for?  
Because Prometheus’s tormentor was an eagle, he was freed by Hercules (who killed said eagle), and eventually made up with Zeus, never once holding a grudge against humans or regretting his decision. It’s called being selfless, a word which probably caused Rand physical pain.

John Colt is Prometheus who changed his mind. After centuries of being torn by vultures in payment for having brought ponies the fires of Celestia, he broke his chains—and he withdrew his fire—until the day when ponies withdraw their vultures.
 

Nice to see Sunset represent Promethium

Prometheus, the first thief! He stole fire from the gods!
 
He couldn’t fence it, though. It was too hot.

Woo, promethium!  
Favorite generic fuel source of the 41st millennium!