Declension table of ?mahātantra

Neuter	Singular	Dual	Plural
Nominative	mahātantram	mahātantre	mahātantrāṇi
Vocative	mahātantra	mahātantre	mahātantrāṇi
Accusative	mahātantram	mahātantre	mahātantrāṇi
Instrumental	mahātantreṇa	mahātantrābhyām	mahātantraiḥ
Dative	mahātantrāya	mahātantrābhyām	mahātantrebhyaḥ
Ablative	mahātantrāt	mahātantrābhyām	mahātantrebhyaḥ
Genitive	mahātantrasya	mahātantrayoḥ	mahātantrāṇām
Locative	mahātantre	mahātantrayoḥ	mahātantreṣu

Compound mahātantra -

Adverb -mahātantram -mahātantrāt