WARNING: The following contains spoilers for Venom #30 by Donny Cates, Luke Ross, Jesus Aburtov, and VC's Clayton Cowles, on sale now.
Eddie Brock's Venom and his son, Dylan, just returned home after spending a year in a different universe that was originally controlled by a symbiote god named Codex. Under this corrupted version of Dylan. Venom and his son helped Agent Venom and the symbiotic heroes of this universe defeat Codex and loosen his grip on the world, restoring it to a normal state.
While Venom, Brock, and Dylan had to spend a few years on Earth-1051, Reed Richards was eventually able to reconfigure technology from Mac Gargan's Virus suit into an interdimensional portal to get them back home in Venom #30. However, the villain better known as Scorpion didn't make the return voyage. Instead, he stayed imprisoned back on Earth-1051 for his crimes in two different dimensions.
While he's gone by many names, Mac Gargan has terrorized Spider-Man and the rest of the Spider-Verse since he was introduced in Stan Lee and Steve Ditko's The Amazing Spider-Man #19. After briefly taking control of the Venom symbiote, Gargan and Brock have had a tense, at best, relationship, that only deteriorated after Gargan was partially paralyzed during Absolute Carnage.
After turning old Stark and Green Goblin technology into his Virus armor, Gargan's attack on Venom resulted in an interdimensional portal malfunctioning which sent him, Venom, and Dylan tumbling into another dimension.
While Gargan was stuck on Earth-1051, he made a deal with Codex to bring him his Eddie and Dylan. Codex gave Gargan a powerful new symbiote to complete his task. This green symbiote came with claws and a tail, letting Gargan become Scorpion once again. But this version of Scorpion may have been the most powerful version of the villain we've seen yet. He easily slices through Wade Wilson and other symbiote-heroes in the Earth-1051 universe. Luckily, Codex can't account for Dylan's power, and he destroys the new Scorpion symbiote with the wave of a hand.
Venom tells Gargan they'll spare his life if he leads Agent Venom resistance forces into Codex's HQ. He does just this, which results in Dylan getting close enough to Codex to disrupt his connection to Knull which essentially turns him back into Dylan Brock before falling into a deep coma. While Codex is fighting with his forces against Agent Venom and the resistance, Gargan slips away and finds his Virus armor. He attacks Venom in one more last-ditch effort to intact his revenge, but Earth-1051's Reed Richards shuts his attack down in a quick, efficient fashion.
Gargan is subsequently put behind bars for at least the duration of Venom and Dylan's stay on this other Earth. And when those two make their return trip to the main Marvel Universe, Gargan is left in his other-dimensional cell.
This certainly won't be the last time we see Mac Gargan and the Scorpion, but it's not clear how soon he might crawl his way back into the Marvel Universe. Considering how close the heroes of Earth-1051 got to Venom and his son, it's not hard to imagine them showing up to help Eddie in the upcoming King In Black crossover, and they could even use the occasion to put Gargan back in a cell that's a little bit closer to home.