Along the way he picked up a variety of weapons, including a gun that fired 'energy harpoons.' In one dimension he encountered Kistur, the leader of an intergalactic gang of criminals who was armed with one of the android Darkhawk bodies created by Dargin Bokk. Kistur asked Little Sky to join the gang so they could use his powers to plunder other dimensions. Little Sky refused and Kistur tried to kill him, but Little Sky fought back and ended up accidentally shooting Kistur's Darkhawk amulet, the focal point of his powers, out of his chest. The loss of the amulet killed Kistur's Darkhawk body, and Little Sky removed and donned Kistur's body armor for further protection. Worried that Kistur might revive, Little Sky attempted to destroy the amulet, but when that failed he discarded it in another dimension.
Little Sky eventually managed to return to Earth, opening a portal to a museum in New York City that Chris Powell and his family were touring. Powell transformed into his Darkhawk persona, and Portal, mistaking Powell for a reborn Kistur, attacked. Darkhawk managed to incapacitate Portal, who was put in federal custody. Portal had been injured during the fight and was placed in a hospital under the guard of Captain America. The U-Foes wanted Portal to take them to a dimension they'd once happened upon while they were exiled from Earth, and they attacked the hospital. Captain America, Darkhawk and Daredevil defeated the U-Foes, but Portal revived and escaped to another dimension during the fight.
Portal surfaced again to retrieve his weapons and equipment from federal custody. He was targeted by the Brotherhood of Evil Mutants lead by Toad, whose member Sauron brainwashed Portal into assisting them. He was rescued by Darkhawk, Spider-Man, and Sleepwalker, after which he escaped again.
Portal would later return as Darkhawk's ally, protecting New York in his stead at a time when Darkhawk seemed to be dying and needed time to recuperate. During this time, Portal was targeted by Shaper, a superhuman snuff artist who'd targeted Darkhawk for death but went after Portal instead. Meanwhile, members of the Mahari race, another alien species from the same home world as Kistur, took control of the Darkhawk ship in a plan to avenge Kistur. They reanimated Kistur in a redesigned Darkhawk android as Overhawk, and went after Portal's family. In the end, Portal and Darkhawk managed to prevent them from destroying the Earth.
Portal is not a criminal, and cannot truly be called a villain. He is not so much evil as amoral, mistrustful of others because of his being harassed by those who would exploit his mutant abilities. While he may return a favor to those who have helped him, as he did by retrieving Spider-Man when Sleepwalker had him freed from Sauron's mind control and filling in for Darkhawk because of their past understanding, he is otherwise a loner who is not generally inclined to heroism. He will do whatever he feels he must to survive, although never more than necessary, such as when he used sleeping gas to subdue the technicians studying his Darkhawk armor, not needing to kill them.
He seems to possess some talent for finding dimensions he has been to before, yet he could not immediately find Earth again once he first got lost in the dimensional planes. Presumably, then, Portal has a kind of extrasensory "marking" ability, allowing him to record the space/time coordinates of a dimension while he's present in it, so that he could return to it again in the future if he chooses. He couldn't automatically return to Earth because he hadn't consciously "marked" it before leaving. Portal is capable of using his powers for teleportation, traveling instantly across about a few miles within a single dimension. Trying to transport himself more than a few miles in one jump, however, will destabilize the portal and send him off into another dimension, even if he's trying to stay anchored in one.
Portal has also been shown to be able to home in on other people who have gone through one of his portals, opening a new gateway to retrieve or follow them if necessary. He used this ability to rescue Spider-Man from the dimension he had thrown the wall-crawler into while under Sauron's control.
Portal is also armed with a wide variety of alien weaponry, including a huge gun that shoots 'energy harpoons', and a suit of body armor he stole from a dead Darkhawk android that's been outfitted to allow him to survive in space.
Little Sky also has an unknown quantity of gymnastics training.
He's also visited planets in unnamed dimensions, such as: