Declension table of ?śastavya

Neuter	Singular	Dual	Plural
Nominative	śastavyam	śastavye	śastavyāni
Vocative	śastavya	śastavye	śastavyāni
Accusative	śastavyam	śastavye	śastavyāni
Instrumental	śastavyena	śastavyābhyām	śastavyaiḥ
Dative	śastavyāya	śastavyābhyām	śastavyebhyaḥ
Ablative	śastavyāt	śastavyābhyām	śastavyebhyaḥ
Genitive	śastavyasya	śastavyayoḥ	śastavyānām
Locative	śastavye	śastavyayoḥ	śastavyeṣu

Compound śastavya -

Adverb -śastavyam -śastavyāt