Declension table of ?kṛṣṇaka

Masculine	Singular	Dual	Plural
Nominative	kṛṣṇakaḥ	kṛṣṇakau	kṛṣṇakāḥ
Vocative	kṛṣṇaka	kṛṣṇakau	kṛṣṇakāḥ
Accusative	kṛṣṇakam	kṛṣṇakau	kṛṣṇakān
Instrumental	kṛṣṇakena	kṛṣṇakābhyām	kṛṣṇakaiḥ kṛṣṇakebhiḥ
Dative	kṛṣṇakāya	kṛṣṇakābhyām	kṛṣṇakebhyaḥ
Ablative	kṛṣṇakāt	kṛṣṇakābhyām	kṛṣṇakebhyaḥ
Genitive	kṛṣṇakasya	kṛṣṇakayoḥ	kṛṣṇakānām
Locative	kṛṣṇake	kṛṣṇakayoḥ	kṛṣṇakeṣu

Compound kṛṣṇaka -

Adverb -kṛṣṇakam -kṛṣṇakāt