Watchtower Key

[Baldur]

Maybe I've missed it I've not 100% looked round the fishery et still got the docks to do but I cant seem to find it anywhere. I waited for more content but ironically waited too long and now the entrance above the door you used to have to jump through is now blocked. Anyone found it and if so.... help

[HarkyCat47]

A bit of spoiler for the current ending.

You can get the key by using the new fast travel/mirror world mechanic.
Go to the mirror world and find the Fishery mirror. There you enter a new room, where you can find the watchtower key.