What did henotheism mean in cults devoted to Isis, Serapis, and Sol?

In the context of Hellenistic religion, henotheism refers to the worship of a single god while acknowledging the existence of other deities. Within the mystery cults devoted to Isis, Serapis, and Sol, this theological tendency functioned as a way to unify diverse divine figures under the supremacy of one god.12

• Isis: She was regarded as the essence of all pagan goddesses, embodying their various attributes and powers.2
• Serapis: His cult served to unite multiple deities—including Zeus, Pluto, Dionysus, Asclepius, Helios, and even the Jewish god YHWH—into a single, overarching divine figure.2
• Sol: In the religion of Sol, an elaborate syncretistic theology was developed to assert that all known gods from various nations were merely provisional names for the sun god.2

By elevating these deities as masters over the stars and fate, these cults offered followers a path to liberation from the deterministic influence of the cosmos.2