July 9, 2025 1:45 AM (GMT+2) I saw things at the bottom when almost fully draining it. However, to keep draining it I would need more space to put the water. There is a “reserve tank” in the Pump room, but I don’t know how to use it. The Pump System User Manual doesn’t help either.

Furthermore, there’s a staircase to get to the bottom, but it was on the opposite side from where I was. I still don’t know how to get there, even less with all the water drained.

This is a long shot, but what I could see at the bottom vaguely reminded me of the “shore of white sand” in The great Alzara (1st time). It could also be related to the “dark waters”.

July 11, 2025 1:06 AM (GMT+2) Given that the Pump room apparently can be powered by steam (see Rooms that have a use for steam power), perhaps that’s what I’m missing to be able to use the reserve tank and fully drain the reservoir.

July 24, 2025 1:51 AM (GMT+2) Two very relevant things have happened related to this:

1. I now have access to the other side of the Reservoir, which is the side that has stairs to go down to the bottom.
2. I can freely access the underground whenever I want, without needing to drain the fountain (or needing to draft the Tomb).

With this, the only thing remaining is to connect the Pump room with the Boiler Room and test my reserve tank hypothesis.

July 27, 2025 2:55 AM (GMT+2) I managed to connect the Pump room with the Boiler Room, and indeed it let me use the reserve tank. As such, I could drain the Reservoir completely. I accessed it through the side which has the stairs and reached the bottom. There were a lot of trunks which need a key to open them (the hammer does not work). They had different symbols and colors, see Trunks at the bottom of the reservoir.

Since I reached the bottom and saw what’s there, I’ll mark the mystery as semi-solved. I’ll mark it as solved when I figure out what’s up with the trunks.

August 1, 2025 1:21 AM (GMT+2) The trunks just seem to have some rewards in them. There’s a whole logic puzzle involving a lot of memos, but in the end I think a lot of brute-forcing is needed. As of now, I’ve already obtained 3 allowance tokens and a Sanctum Key. There’s a memo that seems to imply that’s all there is. But I cannot be sure because perhaps another memo says that the other memo was false. So I’ll just keep opening trunks with my leftover keys at the end of each day.

August 16, 2025 11:25 PM (GMT+2) I opened all the trunks. There was nothing more there. I’ll consider the mystery solved.