A mutant, the Blob claims to be unmovable. He possesses an extreme amount of pliable body mass, which grants him superhuman strength and his own gravitational pull. Possessing the mindset of a bully, he mostly uses his powers for petty crime and as a member of the Brotherhood of Mutants and Freedom Force.
He is one of the most prominent, long-running mutants to be de-powered as a result of the Decimation storyline.
He later winds up in prison, but is freed by Mystique in order to recruit him into her incarnation of the Brotherhood. He becomes part of the plot to assassinate Senator Kelly, the event which leads to the apocalyptic alternate future of Days of Future Past. He also battles the Avengers as a member of the Brotherhood. With Unus, he battles the Hulk. With the Brotherhood, he battles the X-Men once more. He witnesses the apparent death of Unus, then goes berserk and attacks Spider-Man and the Black Cat.
He remains with the Brotherhood, becoming a special operative of the federal government when the Brotherhood is reformed as the government-sponsored Freedom Force. On the team's first mission, they help capture Magneto. They then battle the X-Men in San Francisco. Blob also participates in Freedom Force's capture of the Avengers for the federal government. With Freedom Force, he attempts to capture Rusty Collins, then battles X-Factor. With Freedom Force, he battles the X-Men in San Francisco, and later assists in the attempt to arrest the X-Men in Dallas, battling the New Mutants in Dallas as well. He battles X-Factor again, and with Pyro and Spiral he battles Daredevil in an attempt to capture a young mutant. He again attempts to arrest Rusty Collins, fighting the New Mutants again. He joins Avalanche and Pyro in attacking Avengers headquarters. With Freedom Force, he finally captures Rusty Collins and fellow New Mutant Skids. He helps to capture Cable, but is defeated by Cable and is defeated by Sunspot during an attempt to recapture Cable. With Freedom Force, he assists in thwarting a jailbreak from the Vault.
After Freedom Force's dissolution, the Blob participates in other versions of the Brotherhood, including one led by Toad and another led by Professor X; the Blob takes over as leader of the latter when Xavier leaves.
The psychic entity Onslaught later recruits Blob, vastly upgrading his powers and abilities (in his powered-up state, his mutation becomes virtually identical to those of Phat). During this time, the Blob fights the various members of X-Force and is soundly defeated in each encounter. Months later, a powered-down Dukes joins the new Brotherhood led once again by Mystique, alongside Toad, Sabretooth, and the daughter of the original Mastermind.
When Exodus recreates the Brotherhood of Mutants, Blob offers to join but is quickly dismissed by Exodus, who considers him useless. This is a major blow to Dukes's already weak self-esteem, for which he seeks the counsel of therapist Sean Garrison. After a session, Blob attacks the Xavier Institute, though he is defeated by the combined efforts of the New Mutants and the Hellions. He is then arrested by S.H.I.E.L.D..
Blob later resurfaces as a member of the X-Cell, a group of depowered mutants that blames the government for the loss of their powers, attacking Mutant Town in defiance of the Decimation. After mistakenly getting into a fight with Rictor and Multiple Man and getting in a cheap shot on Rictor, he stole a car. With fellow X-Cell member Fatale, he attempted to flee, eventually hitting an open manhole (left open earlier in the day by Strong Guy and Wolfsbane) and causing the car to crash leaving Blob hanging from the car. When both of them ran afoul of Marrow, Blob was thrown from the car.
Through unknown means, Dukes loses the excess skin and his fortunes turn in his favor. Now known as Freddie Dukes, he has become a weight-loss guru in Japan, and is to star in an upcoming movie filmed in San Francisco made by Kingo Sunen. However, he is also seen with Magneto and the High Evolutionary.
He can also alter his personal mono-directional gravity field beneath himself to make himself virtually immovable as long as he is in contact with the ground, although an incredible force can uproot him, along with a chunk of whatever he is standing on. The only beings on record to have been able to move the Blob against his wishes are the Hulk Juggernaut and Strong Guy (powered-up near his limit by absorbing kinetic energy), although Colossus has managed to lift Dukes by digging underground and raising the piece of earth Dukes stands on, stating this as an exception to his immovability. Despite his morbidly obese appearance, the Blob's speed and agility is that of a fairly athletic male of normal stature, a fact which frequently catches his opponents by surprise.
The Blob's superhuman strength has greatly increased over the years, in a manner similar to that of the Thing. This improvement is said to be a result of his ongoing mutation.
The Blob is vulnerable to attacks directed at his face, as his eyes, nose, mouth and ears do not have the same protection as the rest of his body. Dukes is also susceptible to psionic attacks and psychic manipulation, and he can be incapacitated by sensory assaults; for example, Banshee was able to render Blob unconscious solely through the use of his sonic scream. On another occasion, Sleepwalker defeated the Blob by using warp beams to wrap a steel girder around the villain, crushing his blubber and causing him great physical pain. The Hulk once took the opposite approach, harming the Blob by grabbing and stretching his flab. While he is all but invulnerable to direct kinetic attacks, such as punches, kicks or gunshots, he is susceptible to concussions and other harm resulting from sufficiently powerful impacts, as Daredevil knocked him out by dropping a massive bell on him.
Dukes can be incapacitated by drinking alcohol, although due to his immense mass, it requires a great amount.
McCoy considered Blob's mutation useless which enraged Blob. Dukes freed himself, and attacked his experimenter. Havoc came to McCoy's rescue, but Dukes proved to be even too much for the Prelate to handle. His pseudo freedom was fleeting for moments later the head of the pens, Havoc's older brother Cyclops, showed up to deliver a searing optic blast that would put him back in his place.
When the Age of Apocalypse was revisited in the 10th anniversary, Blob was a member of Sinister's team known as Sinister Six. It appears that McCoy had his powers altered in a manner that allowed Blob to project his gravitational field outward. When the Sinister Six met the X-Men in battle, Dukes' new powers were used to sweep the X-Men off their feet with the Silver Samurai receiving a double dose. Quicksilver attempted to fell the behemoth with multiple punches, but Dukes remained standing regardless of how many hits he got in. It was not until Rogue stepped in with a punch that had the power necessary to overtake him that the mammoth would topple over. Following the Sinister Six's defeat, Psylocke was able to undo his mind control.
In the Ultimate Universe, Blob is a member of the Brotherhood of Mutants. His powers are similar to that of his Earth-616 counterpart, although he has been moved by a helicopter during the Weapon X saga, suggesting that he may be less powerful. He seems to eat constantly, and is often seen browsing the internet or chatting to people via instant messaging. One such incident sees the Blob pretend to be a female model/physicist named Naomi, who cyber-seduces the X-Man Beast — leading to the discovery of Magneto's survival and, eventually, to the Ultimate War saga.
Unlike his Earth-616 counterpart, the Ultimate version of Blob may very well have additional superhuman-eating powers as part of his mutation, as not only has he threatened to actually eat his enemies alive, but it was expressly stated that he had personally consumed all of the Weapon-X computers in a matter of moments when the Brotherhood invaded the Weapon-X compound to rescue the X-Men. Also, his real name is Franklin (Frank).
It has been revealed in Ultimate Spider-Man #120 that Blob is the estranged genetic father of Liz Allan, who had recently discovered her mutant abilities; he claims to have impregnated her mother while working for a circus sideshow.