[3] Bastion attempts to access secret files and operate Cerebro, but the supercomputer activates a computer virus to erase this information rather than letting it be stolen.
Cerebro creates a body for itself, escapes Bastion's headquarters, and tries to follow its original programming literally: find, catalog, and register mutants.
Eventually they encounter Cerebro and his X-Men, who are attempting to destroy the government's mutant tracking satellite, regardless of the potential threat to human life once its radioactive core is breached.
Wolverine's enhanced senses confirm Shadowcat's suspicions that this "Xavier" is an impostor, and the real X-Men realize that if Corbeau's satellite is launched, then Cerebro won't be collect mutants before humans find them.
By doing this, it becomes an even more powerful cybernetic monster, and only the real Charles Xavier is able to subdue Cerebro, purging its systems and destroying the superpowered robotic body it had created.