pre-noun adjectival
Rare literary pre-noun adjectival (rentaishi) meaning 'odd' or 'strange'. It directly modifies a noun and is not used predicatively. Modern Japanese would more often use 奇妙な or 変わった.
彼は奇なる発想で周囲を驚かせた。
He surprised everyone with his odd ideas.
その奇なる風習は今ではほとんど見られない。
That strange custom is hardly seen nowadays.