Properties
Wondrous item, uncommon. While carrying the key, a creature has advantage on ability checks using tools to operate locks, valves, or floodgates. Once per dawn as an action, the bearer opens or closes one nonmagical water-control mechanism within 30 feet that the bearer can see; a physically destroyed mechanism cannot be restored or operated this way.
Lore
Each branch corresponds to a tide once observed beneath Saint Orra’s abbey. The wave-shaped ring trembles when a sealed chamber is taking on water.
Game Master guidance
The key does not open unrelated doors automatically, though it still grants advantage if a door’s lock is integrated with a waterworks system. It cannot override magical control or move a mechanism larger than a building.
Related use
The item is designed as a memorable reward rather than a requirement for later play. A party without it can solve every related scene with the listed checks, tools, spells, or environmental choices.