MTG Salvation

When Hogaak,Arisen Necropolis is cast from the graveyard, does he technically enter the battlefield from the graveyard and if so does him being cast via the graveyard and entering the battlefield trigger a
Prized Amalgam

Casting from the graveyard is not entering from the graveyard. That is why Prized Amalgam looks for both. So yes. When you cast hogaak from the graveyard it will trigger Prized amalgam ability for whenever you cast a creature from your graveyard.

So if you cast it from your graveyard where does it enter the battlefield from?

And thanks for clearing that up i forgot prized checked for both.

You cast Hogaak, which means it goes on the stack as a spell. As such, when it resolves, it enters the battlefield from the stack, just like any other creature spell you cast.