Sentence:  There is also an in-depth discussion of Celtic deities and the Celtic way of life and worship, so that an intermediate practitioner can expand upon the <WSD>spellwork</WSD> to build a series of magical rituals. 
Meaning of the word marked with <WSD> tags:  The formula or formulation of one or more spells or enchantments; the individual parts constituting such a formulation; the inner workings or structure of a spell.