X-Men #14 (1965) introduces the Sentinels, giant mutant-hunting robots created by Dr. Bolivar Trask, as well as showing a more mature Jean Grey flying. After their battle with Juggernaut, the X-Men are given time off by Professor X, but during a televised debate against Dr.
Trask, the Sentinels are revealed and turn on their creator and humanity, leading the X-Men to fight their first battle against them. I got this back 11/29/2023 from CGC, please see pics for condition.