Marvel comics, Avengers #185 Key, origin Quicksilver & the Scarlet witch, 1 of 3

Avengers #185 from 1979, 9.4

"The Yesterday Quest!" Part 1 of 3. Plot by Mark Gruenwald and Steven Grant. Script by David Michelinie. Pencils by John Byrne. Inks by Dan Green. Cover by George Perez and Terry Austin. Ever since their first appearance in Uncanny X-Men 4 many years ago, the origin of Quicksilver and the Scarlet Witch has been a mystery to both comic readers and the siblings alike. After Wanda and Pietro arrive in Transia with Django Maximoff, clues to the twins' birthplace and birth parents begin to emerge. Modred the Mystic, the Darkhold, Bova the cow-woman, the High Evolutionary's former citadel, and Wundagore Mountain are all pieces to the puzzle. And the truth seems to lie at the top of the mountain. But there's something else at the top of Wundagore Mountain. Something ancient, something evil.