Declension table of ?mahāyantra

Neuter	Singular	Dual	Plural
Nominative	mahāyantram	mahāyantre	mahāyantrāṇi
Vocative	mahāyantra	mahāyantre	mahāyantrāṇi
Accusative	mahāyantram	mahāyantre	mahāyantrāṇi
Instrumental	mahāyantreṇa	mahāyantrābhyām	mahāyantraiḥ
Dative	mahāyantrāya	mahāyantrābhyām	mahāyantrebhyaḥ
Ablative	mahāyantrāt	mahāyantrābhyām	mahāyantrebhyaḥ
Genitive	mahāyantrasya	mahāyantrayoḥ	mahāyantrāṇām
Locative	mahāyantre	mahāyantrayoḥ	mahāyantreṣu

Compound mahāyantra -

Adverb -mahāyantram -mahāyantrāt