Any hints as to how to get the drain staff?

[Luthius]

Looks pretty good. Good luck with that, and I hope everything goes well. Oh yeah, and...

I hear the door unlocking sound while circling the round/round path but I've no clue what good that actually is (ie. what opens)

It unlocks the nearby sealed gate, but you have to keep circling it until you see the "puzzle solved" red flash. ‎ :P