Both the Tantric tradition and the ancient celtic myths are based around specific figures and characters which form the throughline of most stories and epics. In general, the figures are symbolic, and linked to various aspects of nature - both our innate human nature, and the natural world we find ourselves in.
In reality, deity worship (like polarity work), is simply a way to access and address different qualities within our own lives and inner worlds. It is a way to recognise their uniqueness and significance, and then use this awareness, inquiry and practice to return ourselves to a space of balance & ease within our relationship to Self, to others, and to the natural world around us.
The cultivation of a 'mythic' mindset, whereby we can look at stories, myths, legends and iconography as a way to more deeply understand ourselves and our own innate qualities, is one which has shaped all of our cultures today.
On a deeper level it's a way to begin returning to the root systems we have lost due to caplitalism, colonialism and a disconnect from nature, as many of the deities we'll explore are intricately linked with and supported by the natural world. In fact you could say that they are a personification of the universal Mother herself.