Declension table of brahmāstra

Neuter	Singular	Dual	Plural
Nominative	brahmāstram	brahmāstre	brahmāstrāṇi
Vocative	brahmāstra	brahmāstre	brahmāstrāṇi
Accusative	brahmāstram	brahmāstre	brahmāstrāṇi
Instrumental	brahmāstreṇa	brahmāstrābhyām	brahmāstraiḥ
Dative	brahmāstrāya	brahmāstrābhyām	brahmāstrebhyaḥ
Ablative	brahmāstrāt	brahmāstrābhyām	brahmāstrebhyaḥ
Genitive	brahmāstrasya	brahmāstrayoḥ	brahmāstrāṇām
Locative	brahmāstre	brahmāstrayoḥ	brahmāstreṣu

Compound brahmāstra -

Adverb -brahmāstram -brahmāstrāt