If "inscription" refers to a written message:
* Erasure
* Deletion
* Obliteration
* Removal
If "inscription" refers to the act of writing:
* Ignoring
* Neglecting
* Overlooking
If "inscription" refers to a mark or decoration:
* Plainness
* Simplicity
* Unmarked
If "inscription" refers to a permanent record:
* Temporariness
* Ephemerality
* Transience
The best antonym will depend on the specific context and the intended meaning.