All of these triads are based on the common and pervasive theme of "threes" attributed to ancient Indo-European (and particularly Celtic) cultures. Similarly, ADF uses the common Indo-European themes of a sacred tree (e.g. the Norse Yggdrasil), a "gatekeeper" or opener of ways (e.g. the Norse god Heimdall, the Celtic god Manannan mac Lir, or the Hellenic god Hermes), and a treaty with hostile entities (e.g. the Norse Jotuns or the Celtic Fomorians). In these ways, ADF practice is an attempt to reconstruct earlier Indo-European beliefs and practices by using the records we have of ancient Indo-European cultures, and looking for commonalities among them which can then be applied to current spiritual practice.