Marvel Two-in-One, Vol. 1 #7 (1974)

Name That Doom!
In Central Park, the Valkyrie abducts Alvin Denton. The Thing and Dr. Strange use the crystal of Agamotto to locate the Valkyrie, as they were told in the last issue that she had stolen a magic harmonica from Strange’s Sanctum Sanctorum. In the process, they discover that it may not have been the Valkyrie at all. The Thing flies off to Cobbler’s Roost, Vermont, to question the real Valkyrie. However, the Executioner and the Enchantress stand in his way. The Enchantress reversing Valkyrie's powers and changing her back into Barbara Norris and blowing into the Harmonica to destroy the universe. Only the Thing and Alvin Denton stand in Amora's way. Denton sacrifices his life in order to allow Thing to use the harmonica to restore all the damage done by the two rogue Asgardians. Valkyrie grieves the loss of the man she just rediscovered was her father. (This story is continued in Defenders #20)
Release Date: 1974