Final answer:
The literary device used in the given lines is neologism, which refers to newly coined words, such as 'vorpal' and 'manxome,' created by Lewis Carroll in 'Jabberwocky'.
Step-by-step explanation:
The literary device used in the given lines "He took his vorpal sword in hand:Long time the manxome foe he sought-" is neologism. A neologism is a newly coined word, expression, or usage that has not yet been fully accepted into mainstream language. In this case, 'vorpal' and 'manxome' are examples of words invented by Lewis Carroll for the poem "Jabberwocky" in 'Through the Looking-Glass, and What Alice Found There' (1871). These invented words add to the whimsical and fantastical atmosphere of the poem, challenging readers to interpret meaning through context despite their unfamiliarity.