Declension table of ?iṣṭu

Feminine	Singular	Dual	Plural
Nominative	iṣṭuḥ	iṣṭū	iṣṭavaḥ
Vocative	iṣṭo	iṣṭū	iṣṭavaḥ
Accusative	iṣṭum	iṣṭū	iṣṭūḥ
Instrumental	iṣṭvā	iṣṭubhyām	iṣṭubhiḥ
Dative	iṣṭvai iṣṭave	iṣṭubhyām	iṣṭubhyaḥ
Ablative	iṣṭvāḥ iṣṭoḥ	iṣṭubhyām	iṣṭubhyaḥ
Genitive	iṣṭvāḥ iṣṭoḥ	iṣṭvoḥ	iṣṭūnām
Locative	iṣṭvām iṣṭau	iṣṭvoḥ	iṣṭuṣu

Compound iṣṭu -

Adverb -iṣṭu