The 6th century legendary seer-poet Taliesin tasted the liquid of Inspiration and underwent series of metamorphoses. This was the archetype of bardic initiation and as he changed shape he traced within himself the changes of the cosmic powers. He became the Knower whose words were a mythological map. Celtic mythology is vast and rich, but presents difficulties to interpretation. The present work provides an extensive guide through Celtic mythology in terms of comparisons with other European and Indo-Iranic mythologies. As it proceeds, a map of a deep and ancient mythological and theological structure begins to reveal itself.