Declension table of ?sarasya

Neuter	Singular	Dual	Plural
Nominative	sarasyam	sarasye	sarasyāni
Vocative	sarasya	sarasye	sarasyāni
Accusative	sarasyam	sarasye	sarasyāni
Instrumental	sarasyena	sarasyābhyām	sarasyaiḥ
Dative	sarasyāya	sarasyābhyām	sarasyebhyaḥ
Ablative	sarasyāt	sarasyābhyām	sarasyebhyaḥ
Genitive	sarasyasya	sarasyayoḥ	sarasyānām
Locative	sarasye	sarasyayoḥ	sarasyeṣu

Compound sarasya -

Adverb -sarasyam -sarasyāt