The oddly-acting Odin stands revealed to Thor as the monstrous Mangog, whose sinister plan is to draw the Odinsword from its scabbard and so destroy the universe. The beast fills Thor (and the reader) in on how he came to this point in time: Igron had been banished to the dungeons by the All-Father (issue #212) where he discovered the mighty Mangog miniaturized in #198. Using magic learned from Loki, Igron drew on the life-forces of the inhabitants of Asgard to restore the monster to nearly his full power thus plaguing the Asgardians with a strange lethargy (noticed in #240). When they discovered that Odin was missing, Igron cast a spell of illusion over Mangog and he took the throne as Odin. And now the wizard restores the false form as the Palace Guards enter and battle Thor; while distracted, the Thunder God is laid low by a bolt of the phony Odinforce, and he is taken away for judgment….
Outside the palace, Thor’s friends are gathering large crowds of supporters and they converge on the castle—where they see Thor a prisoner in a massive stock. Odin tortures Thor before their eyes and when the Grand Vizier questions this he is blasted by the fake All-Father. Thor’s friends rise up in protest and "Odin" turns the warriors into animals and causes Sif to age into a hag. The sight of this causes Thor to tear himself free from his bonds. When Igron tries to calm the power-mad monster, Mangog destroys him, causing the illusion spell to cease and the wicked beast to stand revealed to the people. Mangog smashes his way through the palace to reach and draw the Odinsword and Thor pursues. Before he can reach the sword, the monster fades into nothingness without the worship of the people and the Golden Realm is saved.