Warlock #9 (1975)

Warlock refuses to believe that he will become as evil as the Magus but the villain says every word Warlock utters at the same time. Gamora states that she can't interfere just now and that it might be time for someone else to get involved, Pip thinks she refers to him but she is actually communicating with her as of yet unnamed master. Magus can't detect Gamora and the voice of her master reveals that this is a defense the Magus' own nature has given to them. Magus tells Warlock what will happen next (as he remembers it), he will attack Warlock with the Soul Gem and saturate Adam's body with radiation to summon the In-Betweener; three hours after the In-Betweener will appear he will take Warlock to his realm where he will float four centuries, he then will enter his protective cocoon and become the Magus once he leaves it again, he will awake 5000 Years before the time of his meeting with the In-Betweener. He also tells how he conquered Homeworld and created the Universal Church of Truth. The voice of Gamora's master reveals, that the Magus can't see her, because she wasn't there before and thus can't remember her being there staying ignorant of her presence. Twelve seconds before the Magus summons the In-Betweener, Gamora starts her attack but the Magus discovers her just in time telling her, that she can tell her master, whoever he is, that the Magus now knows that he is there and will deal with him in due time. After making clear that he can't trust the Matriarch anymore, he orders all the Black Knights to kill Warlock and his comrades; though he doubts that they can defeat Warlock, he thinks it best to have Warlock occupied until the In-Betweener appears and 2500 Black Knights are just the means. Thanos is revealed as Gamora's master and he joins Warlock and the others to fight by their side (which is unknown to the Magus).