The Heroes of Lallor first appeared in Adventure Comics #324 (1964) and aside from a story in which Beast Boy died (Adventure #339) and a smattering of appearances for Duplicate Boy as Shrinking Violet's boyfriend, they've been pretty much relegated to the role of cameos in group shots at fancy functions (like Legion marriages) or in the background in the more epic fights (like the Great Darkness Saga). Their origin tale was reprinted in Batman #238 (1972).
An accidental atomic explosion on the planet Lallor in the middle of the 30th Century affected the genes of five couples living near the site. Each of the five children born to these families possesses unique powers:
Duplicate Boy (Ord Quelu) can mimic any other individual's powers. He can duplicate different powers at the same time, as evidenced by shrinking himself to chase Shrinking Violet and then duplicating Superboy's heat vision to set fire to a bundle of sticks to scare off an animal trying to attack her.
Beast Boy (Ilshu Nor) can change into animal forms.
Life Lass (Somi Gan) can animate inanimate objects;
Gas Girl (Tal Nahil) can change into a sentient gas form; and
Evolvo Lad (Sev Tcheru) can evolve into more advanced or more primitive forms.
Exiled from Lallor by a dictator, the five went to Earth, where they were briefly tricked by a man named Doctor Marden King into battling the Legion of Super Heroes, in attempt to seek vengeance for his brother Jungle King's death. The five returned to their planet as heroes, and although Beast Boy died an outlaw, they have remained the principal champions of justice on Lallor. Duplicate Boy and Shrinking Violet were romantically involved for a while.
5 Years Later
All members did wind up appearing in the 5 Years Later era (five years later). Life Lass as a member of the United Planets militia, and then Lallor fell to the Khunds. Apparently under Khund control, the Heroes appeared in Legion of Super-Heroes.
Post-Zero Hour, a few of them showed up in the series Legionnaires. Beast Boy and Gas Girl, with the former Arm-Fall-Off Boy, and Splitter. However Evolvo-Lad was in another team called Workforce and was not part of the Heroes of Lallor in this continuum.
Threeboot Legion books made use of Lallor, but only Evolvo-Lad was ever seen as of Brainiac 5's ally's.