Declension table of mantrasiddhi

Feminine	Singular	Dual	Plural
Nominative	mantrasiddhiḥ	mantrasiddhī	mantrasiddhayaḥ
Vocative	mantrasiddhe	mantrasiddhī	mantrasiddhayaḥ
Accusative	mantrasiddhim	mantrasiddhī	mantrasiddhīḥ
Instrumental	mantrasiddhyā	mantrasiddhibhyām	mantrasiddhibhiḥ
Dative	mantrasiddhyai mantrasiddhaye	mantrasiddhibhyām	mantrasiddhibhyaḥ
Ablative	mantrasiddhyāḥ mantrasiddheḥ	mantrasiddhibhyām	mantrasiddhibhyaḥ
Genitive	mantrasiddhyāḥ mantrasiddheḥ	mantrasiddhyoḥ	mantrasiddhīnām
Locative	mantrasiddhyām mantrasiddhau	mantrasiddhyoḥ	mantrasiddhiṣu

Compound mantrasiddhi -

Adverb -mantrasiddhi