In the books of sorrow number 48 Leviathan Rises, it talks of a leviathan, Oryx, and “eating” the traveler, does this connect Oryx to the cabal or is it coincidence that there is more than one Leviathan?
The Leviathan of The a Books of Sorrow is an organic servant of the Light, whereas Calus’ Leviathan appears to be a very large wholly mechanical ship inspired by some kind of land whale native to his home planet. If there’s a connection, I’d be surprised. It certainly would be an interesting development.
In that same verse it refers to the Leviathan as “The Old Priest” by which I believe it means a priest of the light and when it says eat the Traveler it means eat it’s light because in the Hive grimoire card the Hive are described with “our great hunger is to pursue and eat that which is not free, and to liberate it with devouring” so it’s saying that they will devour the light and at this point Silverheart has already given a good reply, so I’ll just leave this here.
As @Silverheart said, the Leviathan from the BoS is a gigantivc creature, like that of the one on Titan.
The Leviathan was living in the gas giant Fundament. The concept art that came with the Limited Edition D2 showed the Cabal and their whale eater on a planet which looks nothing like a gas giant. I don’t believe the two are connected. Just the names are similar.
The Leviathan in the BoS is an entity that served the Sky, while Calus’ Leviathan is just the ship where he was exiled to. So I honestly doubt they could be connected at all.