Declension table of ?ṛkva

Neuter	Singular	Dual	Plural
Nominative	ṛkvam	ṛkve	ṛkvāṇi
Vocative	ṛkva	ṛkve	ṛkvāṇi
Accusative	ṛkvam	ṛkve	ṛkvāṇi
Instrumental	ṛkveṇa	ṛkvābhyām	ṛkvaiḥ
Dative	ṛkvāya	ṛkvābhyām	ṛkvebhyaḥ
Ablative	ṛkvāt	ṛkvābhyām	ṛkvebhyaḥ
Genitive	ṛkvasya	ṛkvayoḥ	ṛkvāṇām
Locative	ṛkve	ṛkvayoḥ	ṛkveṣu

Compound ṛkva -

Adverb -ṛkvam -ṛkvāt