"Istukan" is that which is not created by God, invented by man, that which is artificial and not originally natural, that which tempts man to bow down to it as divine.
"Istukan" is anything that substitutes for the true God; that which is dead, soulless, frozen, having no life, producing no life, that which is the opposite of life.
It is a religious, political, etc. fetishism, a fetish; created by "man of sin," an object, an object, the result of his activity, a special veneration, preference, giving priority.
"Istukan" in Scripture means some political, religious, economic model of organization, of the management of society, a certain state system that claims special veneration, cultivates it, supports it, causes fanatical devotion among the nations.
(For example: "Istukans" in history have been some of the many leaders of states or religious beliefs to whom honors have been paid as to a deity)