Giant-Size Avengers#4(1975)

Continued from Avengers Vol 1 135... Following his adventures through time to learn his origins, Vision finds himself transported to the molten heart of the Earth where the Scarlet Witch and Agatha Harkness are the prisoners of Dormammu and Umar. There the Vision battles against Dormammu's demonic minions to save the Scarlet Witch. Meanwhile, in the Temple of the Priests of Pama in Vietnam, Libra and the spectral form posing as Swordsman reveal that Mantis' recent adventures were all orchestrated in order to see if she was fit for the role of Celestial Madonna and if she wasn't, then Moondragon would take her place. Back deep below Earth's surface, Vision manages to free the Scarlet Witch, and the two defeat Dormammu and Umar before being transported back to Avengers Mansion. There the Vision confesses his true feelings for the Scarlet Witch and asks her to marry him, a proposal which she accepts. They meet up with the other Avengers in Vietnam where Immortus has also arrived to play his part in this drama and marry off both Mantis to her Cotati mate and Vision and the Scarlet Witch. However, the ceremony is crashed by the arrival of Kang who has come in one last-ditch effort to claim the Celestial Madonna for himself. Using temporal duplicates of himself, Kang clashes with the Avengers and appears to make off with Mantis; however, it is later revealed that Mantis was with the Avengers the whole time, and the being whom Kang thought he had captured was really one of Immortus' minions: The Space Phantom. With Kang thwarted, Immortus marries off both couples and Mantis and the Cotati being changed into energy forms and leave Earth to be among the stars and find their destiny together.