Flaxan Invasion

In the wake of the Guardians of the Globe's murder, an alien force from another dimension, the Flaxans, pours into Earth. With the veteran heroes gone, the young Teen Team and a rookie named Invincible are left to hold the line. The invaders attack three times, and on each occasion they are beaten back. At first they retreat because Earth's slower flow of time ages them to death, but they steadily engineer countermeasures that make every wave harder to repel than the last.

During the opening assault the Flaxans teleport into the city center and cut down anyone in reach. Invincible rushes in and saves an elderly woman named Maya, though a botched landing badly injures her legs. Atom Eve arrives to deflect a cannon blast aimed at him, and the rest of the Teen Team joins the fight before the Flaxans collapse from rapid aging and flee.

Three days later a second wave returns led by the same Flaxan Invincible had scarred, now decorated and no longer aging. Robot deduces they have found a way to resist Earth's time, and the invaders, having studied the team's powers, gain the upper hand. After the Flaxan Leader kills Atom Eve to avenge his earlier defeat, a furious Invincible breaks free and damages the leader's wristband, restarting his aging. Robot spots the weakness, secures a wristband, reads its frequency of forty-nine thousand kilohertz, and emits a signal that destroys them all, driving the Flaxans off once more.

The third invasion arrives fully immune to Earth's timestream, with the leader commanding from inside a powerful mech. Robot declares the city lost and floats a nuclear response the others reject. The mech-clad leader overpowers Invincible and prepares to finish him until Omni-Man crashes in, shrugs off every attack, and drives the invaders into retreat.

Rather than let them escape, Omni-Man tackles the Flaxan Leader through the portal and lays waste to their dimension, killing the leader, slaughtering countless Flaxans, and flattening their cities. He forces surviving scientists to reopen the gateway home, then drops a massive chunk of ground on them as he flies through. The Flaxans are later seen rebuilding and plotting revenge against Omni-Man and Earth. Casualties include Maya, many humans, three Flaxan scientists, and the Flaxan Leader. The event debuts in the first season's second episode.