"Old Entity", known as "Old God" ( () (シン) Koshin) in the OCG, is an archetype of Synchro Monsters based on the Great Old Ones from H. P. Lovecraft's Cthulhu Mythos, and is directly related to the "Elder Entity" and "Outer Entity" archetypes, the three each being a subtype of the larger "Entity" series. Currently, its only members are "Old Entity Chthugua" and "Old Entity Hastorr", with its only support card being "Forbidden Trapezohedron". Both were released as exclusive cards for the Korean releases of Duelist Alliance and Secrets of Eternity.

Community content is available under CC-BY-SA unless otherwise noted.