I completed the two (similar) puzzles to gain the keys to get into the Sphinx. I think I chose the easier of the two puzzles last (unintentionally), making the first one I attempted harder than I expect it would have been had I done them the other way round.
Once in the Sphinx, there was a puzzle with lowering a raising water, and then a long corridor leading to a room with loads of baddies. It took me a fair few tries to beat them, but finally did and picked up the final bit of the Scion. Only to have Natla come and nick all the bits. Tch.
Anyway, I found myself on an island, and spent ages figuring how to progress from the warehouse you there (sans guns – which made the rats annoying), eventually making it through and past a lava section, to find two of Natla’s goons. With them dealt with, I could open up a huge metal pyramid. Onward!