Prepositions "Hen" and "Va" with dative nouns

[linguista420]

Can someone clarify when these prepositions are required and when they are not. I am not seeing the pattern here, and the light bulb notes don't make it clear. Kirimvose.

[tim981145]

Maybe this helps: https://wiki.dothraki.org/High_Valyrian_Adpositions