Declension table of ?ṛdhaṅmantra

Neuter	Singular	Dual	Plural
Nominative	ṛdhaṅmantram	ṛdhaṅmantre	ṛdhaṅmantrāṇi
Vocative	ṛdhaṅmantra	ṛdhaṅmantre	ṛdhaṅmantrāṇi
Accusative	ṛdhaṅmantram	ṛdhaṅmantre	ṛdhaṅmantrāṇi
Instrumental	ṛdhaṅmantreṇa	ṛdhaṅmantrābhyām	ṛdhaṅmantraiḥ
Dative	ṛdhaṅmantrāya	ṛdhaṅmantrābhyām	ṛdhaṅmantrebhyaḥ
Ablative	ṛdhaṅmantrāt	ṛdhaṅmantrābhyām	ṛdhaṅmantrebhyaḥ
Genitive	ṛdhaṅmantrasya	ṛdhaṅmantrayoḥ	ṛdhaṅmantrāṇām
Locative	ṛdhaṅmantre	ṛdhaṅmantrayoḥ	ṛdhaṅmantreṣu

Compound ṛdhaṅmantra -

Adverb -ṛdhaṅmantram -ṛdhaṅmantrāt