Bolivar Trask was an anthropologist who saw the rise of mutants as a threat to humanity. Bolivar was also the father of Larry Trask, who, ironically, is revealed to be a mutant with precognitive powers. Bolivar had realized this, and gave his son a medallion which suppresses his power. Bolivar's other child, Tanya, was also a mutant and her ability to travel through time causes her to vanish. Tanya would be rescued by Rachel Summers in a far future and would become a part of the Askani under the alias Madame Sanctity. Tanya's travels through time would result in property damage to Trask's land. This mysterious situation would only further cement his attitudes toward mutants.
Bolivar decides that humanity has to fight back against the mutants and develops robotic guardians for humanity, known as the Sentinels. His son Larry was protected from the Sentinels' ability to detect the mutant X-gene due to the medallion Bolivar had given him. Bolivar publishes articles on the threat of mutants. One of these articles showed an illustration of mutant overlords keeping humans as slaves. This illustration would become a symbol for human/mutant relations and several years later, Quentin Quire and his Omega Gang would base their appearance on this picture.
Professor Charles Xavier invites Trask for a public debate on human/mutant relations. Xavier's arguments that mutants were just like humans and not evil did not convince Trask and he reveals the Sentinels. Trask and his scientists had apparently created an adaptive, open-ended tactical/strategic programming. Trask was not a very skilled programmer, though, and the Sentinels turn against him, claiming that they were superior to humans. The Sentinels left with Trask and brought him to his first creation, the Master Mold, who orders him to construct more Sentinels.
To stop the Sentinels, Xavier summons his X-Men. The X-Men fight the Sentinels, but Beast is captured. To reveal the X-Men's secrets, the Sentinels tell Trask to use a device to read Beast's mind. Trask discovers that the X-Men were mutants protecting humanity and realizes that he had been wrong. He helps the X-Men defeat the Sentinels by sacrificing himself to destroy the Sentinels' base.
Bolivar's death would not be the end of the Sentinels, though, as Master Mold would return and Bolivar's son, Larry, still unaware of his own mutant status, would follow in his father's footsteps and create new Sentinels to avenge his father.
Later, a relative of Bolivar, Donald Trask, would be recruited by the villain Cassandra Nova to gain control of a group of Sentinels. The machines, now varying in size, will not harm Trask DNA. They obey Donald's orders. However, once Nova is done copying all of Donald's DNA, she kills him and takes over the robots.
Recently, in X-Force, Bastion who has been reactivated by the Purifiers has apparently resurrected Bolivar Trask through use of a Technarch to be part of a team of the world's foremost mutant killers. During the assault on X-Factor, Trask wrested control of himself from Bastion, and after ordering the end of the assault on X-Factor, committed suicide.
- It was revealed in X-Force Vol 3 #3, that Trask's "mutants killed" count is 16,521,618