Hmmm...I've been thinking

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Vestec + Undasis= UNDATEC, the God of [b]Weather [/b]and natural disasters

Arguis + Undasis= [b]Hidden Knowledge, Secrets[/b], etc. The oceans are sometimes thought of being mysterious or hiding secrets, and Arguis is the God of Knowledge. Named Unduis.

Ferghus + Undasis= No idea. But his name would be Fergasis.

Evelynn + Undasis= No idea. Named Undalynn.

Astarte + Undasis= [b]Elemental Magic[/b]. The water is an element, and Astarte is magic. Or perhaps Water Magic? Named Astasis.

Vowzra + Undasis= No. Undasis would sooner dry up the oceans. 

Escre + Undasis= [b]Sea-life[/b], possibly [b]Monsters[/b] (because of all the sea-monsters I've been making, which are technically Life). Named Esis.

Sauranath + Undasis= [b]Sea-monsters[/b]. Named Undanath.

Svie + Undasis= [b]Autumn[/b]? [b]Rain[/b]? [b]Weather[/b]? Named Sviedasis.