I think Oryx’s worm could make a return.
In the lore for Bad Juju, Toland talks about a royal secret using death in a chrysalis. This could be Oryx, due to the fact that
A. He is royal
B. When killed in. King’s Fall, he seems to grow something around him as he falls into the rings of SATURN.
Coincidentally, that’s where Titan is. Who’s to say that his body landed on Titan, and the worm came out as the Leviathan in the oceans. It has the appearance of a large worm, so it could be possible, which( would also explain the appearance of the Hive on this moon.
English
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<The biggest sigh exhaled from my body happened when I saw the word Titan pop up. I should've seen it coming but nonetheless I was taken aback. No. The answer is no. Oryx is dead, Savathûn doesn't want him back, Oryx's Worm was in the Touch of Malice, either destroyed or taken by Eris. Oryx's body floated towards Saturn, not Titan, which is in the opposite direction. Gravity disproves the entire theory. Not to mention that Oryx's plan involved the ToM anyway, making any other plan redundant and stupid in his eyes.>