As far as behavior goes I’m thinking that Hephaestus uses spine backs to transport vast amounts of blaze and chillwater from giant whale like machines, that are used to transport stuff across oceans, then it fills up and heads for shore and the nearest cauldron since the whales are to big to come to shore.
As well as it having a crate like shellwalkers or behemoths have and if you make a move for to he will clutch his arms around it like “No, this is mine” and get really angry if you knock it off to destroy it. He wants to defend it so he always shows his back to you hence the gun on the tail.