Declension table of ?pratyastra

Neuter	Singular	Dual	Plural
Nominative	pratyastram	pratyastre	pratyastrāṇi
Vocative	pratyastra	pratyastre	pratyastrāṇi
Accusative	pratyastram	pratyastre	pratyastrāṇi
Instrumental	pratyastreṇa	pratyastrābhyām	pratyastraiḥ
Dative	pratyastrāya	pratyastrābhyām	pratyastrebhyaḥ
Ablative	pratyastrāt	pratyastrābhyām	pratyastrebhyaḥ
Genitive	pratyastrasya	pratyastrayoḥ	pratyastrāṇām
Locative	pratyastre	pratyastrayoḥ	pratyastreṣu

Compound pratyastra -

Adverb -pratyastram -pratyastrāt