Peter Petruski was a chemist who was working on an extremely adhesive multi-polymar. With it he created a paste-spraying gun to commit crimes and called himself Paste Pot Pete. He battled the Fantastic Four a few times before joining forces with the Wizard, Sandman, and Medusa to form the Frightful Four. The team was defeated by the fantastic Four, but came back several times with different members.
During his time with the Frightful Four, Petruski changed his name to the Trapster, as his former supervillain name, Paste Pot Pete had been the butt of many jokes and taunts from his enemies. Trapster's paste guns could fire a variety of adhesive traps, including exploding paste balls, lubricates, swing lines, and shooting discs. He also has equipped himself with gloves and boots that enable him to climb walls and ceilings.
Trapster has often sought independent recognition, battling virtually every "street-level" hero in the Marvel Universe either by design or by opposition to some criminal scheme. Trapster once even defeated Daredevil in single combat The victory proved short-lived, as Doctor Doom interrupted his fight in a campaign of his own against Daredevil, and shortly thereafter the hero would avenge his defeat. Trapster also attempted to raid the Baxter Building (just before it was destroyed by Doctor Doom II) while the Fantastic Four were away participating in the Secret Wars, but embarrassingly fell victim to the security systems and the robot receptionist, thus becoming the first villain to be defeated by an empty building. However, he had a moment appreciated by the heroes when he was convinced to free Captain America, who was snared by Baron Heinrich Zemo's powerful Adhesive X, by inventing the first ever means to neutralize the previously uncounterable chemical.
Saddened by constant defeats, Trapster would seek out the Tinkerer's aid in redesigning his arsenal. Adding wrist-pumps for his glue weaponry and a bandolier of various explosives and gimmicks, Trapster joined forces with the mutant villain Whirlwind in a bid to defeat Captain America. Despite his improved arsenal, both villains were defeated.
The Trapster found his moment of victory over Spider-Man when he teamed up with the Shocker but before the duo could finish Spider-Man off, their employers said their payment would be doubled if they left Spider-Man alone and they complied. He would later defeat Spider-Man in one-on-one combat after being enlisted to battle the wall-crawler as part of the Acts of Vengeance conspiracy; it was only through merest quirk of fate that Spider-Man even survived the battle. However, when the Trapster learned of Spider-Man's survival and returned to finish the job, he would find the web-slinger now in possession of cosmic powers (eventually revealed to be a manifestation Uni-Power) with which Pete was easily defeated.
Later on, during the Identity Crisis story, the Trapster would be hired by Norman Osborn to kill a man and make it seem like Spider-Man did it, and in order to cover this up Osborn put a price on Trapster's head, attracting assassins like the Hand and his previous ally Shocker. Trapster unknowingly teamed up with Spider-Man who was using the alias of Dusk, reasoning that the currently-lone Trapster would need an ally and someone to talk to in his currently vulnerable state. In an attempt to get back at Osborn, and would eventually confess his murder to the police in order to remove Osborn's reason for wanting him dead (although he kept the identity of his employer secret in case he needed it later).
During his tenure with a later Frightful Four incarnation (including Hydro-Man and the mysterious Salamandra), the Wizard, tired of Trapster's failures and his general sniveling, callously sealed the villain in a repeating time-loop, a trap from which he can "never escape." However, Petruski did indeed escape.
During the Secret War storyline, Trapster was enlisted by Lucia Von Bardas, the former prime minister of Latveria and placed in her secret army of technology-based villains. She sent the army against Wolverine, Spider-Man, Luke Cage, Daredevil, and Captain America, the five heroes Nick Fury had sent to Latveria to stop Lucia’s secret criminal funding. When the battle started to turn in favor of the heroes, Lucia turned all the armor of her technology army into a bomb. Nick’s unknown agent Daisy defeated her and the armor army’s lives were saved. Pete escaped the heroes in the resulting battle between Nick Fury and Wolverine.
He appeared in Brand New Day as one of the villains in the bar, and later fighting Spider-Man in the Brand New Day Extra one-shot.
During the Dark Reign storyline, Trapster later showed up in an alliance with the criminal named Zodiac.