The Royal Arcade opened in 1870, but in 1892 Gaunt's clock was installed with two 7-foot giants on either side striking the hour. These are modelled after those in the Guildhall in London that date back to 1708.
"Several myths surround Gog and Magog, including one where they were guards of the underworld and gods of dark spirits. As the prophecy goes, once when Gog and Magog return to war, the war will end."
royalarcade.com.au/pages/history
Interestingly enough, Gog and Magog also appear in ancient Biblical prophecy (Ezekiel 38-39). In the apocalyptic book of Revelation 20:7-10, both Gog and Magog relate to evil forces or nations who unite with Satan in a great final conflagration. It ultimately leads to the destruction of evil and the establishment of God's Kingdom on earth.
en.wikipedia.org/wiki/Gog_and_Magog 