The name Primus, prime comes from the Latin word for "first", so I mean there's that. He's also absent from Maldraxxus for some reason, but we know that he was the collective leader of all of the houses there and he was probably really powerful. He leaves behind a bunch of cryptic prophecies and shit. We keep seeing references to the First Ones, like from the Jailer and the Brokers. I can't help but think they must be related.