Who Are the Fatal Five?

Who's This? The match the Legion made.

The facts: In Adventure Comics #352 (January 1967), Jim Shooter had the Legion recruit five (never before seen) criminals to help them fight the Sun-Eater - the Emerald Empress, Mano, the Persuader, Tharok, and Validus. After those events, they decided to stay together as the Fatal Five and have been hounding the Legion through many of the team's incarnations (with occasional changes in roster) including the Silver Age, Bronze Age, Baxter era, 5YL, Reboot and Retroboot. Though they weren't in the Threeboot, they still appeared in other comics during those years, just coming from a different timeline.
How you could have heard of them: They appeared in animation in both Justice League Unlimited and Legion of Super-Heroes, the latter spawning a Validus toy given away with McDonald's Happy Meals in 2007! Oh and in 2019, in Justice League vs. the Fatal Five.
Example story: Superboy Starring the Legion #198 (October 1973), "The Fatal Five Who Twisted Time!" by Cary Bates and Dave Cockrum

In a story that takes place in two time frames, Superboy has been worried about a green UFO giving people sporadic X-ray vision in Smallville, when he spots the Eye of Ekron at the local fair, being used by a fortune teller - or, in reality, the Emerald Empress!

The Persuader is also there disguised as the resident strongman. As Superboy fights them, their resolve is unshaken. The Time-Sorter has already decreed he would lose. Clark grabs the Atomic Axe, but he's suddenly seized by the urge to hit himself with it - it is never not under the Persuader's control (I mean, he has to persuade SOMEthing).

As decreed, Superboy is defeated. Mano missed all the action. In the woods outside of town, a quartet of Legionnaires appears in a time bubble looking for the Fatal Three. They missed all the action too, and now their prey have left with Superboy's body. 1000 years up-time, the other Legionnaires discover that Tharok and Validus have escaped too and suddenly find themselves and their HQ disappearing - Back to the Future-style! And even if the team sent down-time had a future to return to, they soon lose their time bubble when Persuader sends his axe right through it! They're ALL under attack.

We don't see the Empress' face in the Eye very often these days, but brrrrrr. These are some powerful villains. The Eye has unlimited power, Persuader can cut through anything, and Mano has a death touch. And with this Time-Sorter, they've not only defeated Superboy, but prevented the events that brought the Legion together.

It IS true, Karate Kid, and there's really no stopping these guys with super-karate. You four are stranded forever. Meanwhile+1000, Mano joins the Tharok and Validus, claiming he was delayed and didn't go to the past with the rest. Is he a fake, or is the one adamantly asking to be told where his pals hid the Time-Sorter the fake? When Brainiac 5 gets a signal, it becomes clear it's the latter, but the jig is up when the Empress notices Mano's hand touching something without disintegrating it. So it was a QUINTET, after all, one including Chameleon Boy, who else? Before they can slice him in half, Validus appears and distracts them - he's of course an illusion cast by Princess Projectra. Karate Kid takes his chance and chops the statue of Superboy in the middle of Smallville in half, as it contains the Time-Sorter AND Superboy's prone body. Seconds later, Val destroys the infernal machien and up-time, Legion HQ remateralizes. Validus makes a break for it, and down-time, the Empress and Persuader time-port to another era, but at least we've got Tharok and Mano.

They even kind of captured THEMSELVES!

The story is a fun one that shows off how dangerous the Fatal Five are, but also how it's harder to give each of them something to do given the power levels involved. Three of them are side-lined to better focus on the others, and indeed, I think the Emerald Empress and the Persuader have the best shots at going forward as a duo, or even as soloists (which they have done at different points). Easy to see why Tharok would eventually be killed as he does seem surplus to requirements, while Validus' mindlessness makes him difficult to write as anything more than muscle. Mano's almost too powerful - but also, too straightforward - to make him a headliner. Cary Bates therefore chooses to focus on the best two, and in a Legion story where there are a LOT of heroes too, is there room for a villain team in a done-in-one story like this? I do feel like there might have been if Bates had cut the sequence with the escaped gorilla...

Who's Next? Dr. Light's irregulars.