expression, pre-noun adjectival
now gone; no longer existing; lost
A fixed literary expression used before a noun to indicate that something or someone no longer exists, often with a nostalgic or elegiac tone.
I recall the vestiges of the now-lost ancient capital.
Tears fell as I thought of my friend who is no longer with us.
Standard kanji spelling; 無き is the classical attributive form of 無い used in this fixed expression.
Kana spelling is common in modern writing, especially when the classical feel of 無き is not needed.
A fixed phrase combining 今 (now) + は (topic marker) + 無き (classical attributive form of 無い, 'not exist'). The use of the classical attributive 無き instead of modern 無い gives it a literary, nostalgic feel.