Gifts of the sea
Things that have washed up at Pelagia before Raven’s Purge
In the Eastern Cliff of Pelagia (Raven’s Purge) is the Chamber of the Winds, inside which is a stone chest which contains, if there is currently one, the Gift of the Sea. When the PCs arrive, it turns out that there’s something inside that almost everyone agrees wasn’t actually a gift of the sea, being the huge dwarven warhammer Scarnesbane, which is fine. The adventure also says that there have been 4 previous gifts, and doesn’t mention what they were, which IMO is not ;-) .
(Also, if it’s a gift of the sea, it shouldn’t be at the top of a tower where all four winds blow fiercely; given Pelagia’s likely location on the Eastern coast of the Ravenlands, probably only one of those winds unambiguously comes from the sea. Instead, you should unlock a passageway to a sea cave, preferably one which is completely submerged except at a really rare low time, like a neap tide or something. If you haven’t already decided how many moons your world has, btw, multiple moons make for more extreme tides. Ideally the entrance to the sea cave from the sea should be blocked by iron bars or maybe coral or some kind of porous stone, like the sort that whiners build, so it’s obvious that if a solid object appears and is a gift of the sea, it’s a miracle. How impressed people would be by miracles in a world where there’s magic, though, is down to you.)
So, here’s a few things I think could have been Gifts of the Sea before, or claimed to be at one point. (Pelagia is said to have been the place of landfall of the humans back in year 0, so I would have thought there would be a permanent delegation of humans from Farhaven, as it’s one of the most significant religious cities for the Congregation of the Serpent. I suspect they disagree with the local druids about what and what doesn’t count as a Gift of the Sea. Someone back in Farhaven may have a book full of apocryphal gifts, which were once recognised but have since been disowned.)
And given that there are four winds and four towers, the fourth Gift should be special somehow.
Neyd’s Staff of Erosion
We know that Neyd mapped and named all of the rivers. Legends say that before Neyd turned up, all of the land was basically a swamp, but Flow helped Neyd teach water how to get its act together. Legends also say that the planet used to be much smaller, but the dwarves conjured up rock and made it bigger, until eventually they’ll reach the sun. So a logical extrapolation is that the dwarves were efficiently, but soullessly, building a perfectly spherical planet, and of course any surface water has nowhere to go at that point.
This is almost certainly nonsense (although dwelvers may fervently believe the perfectly spherical planet idea, and claim that they remember it). What’s more likely is that dwarves going around making stone are likely to just conjure up crude slabs and job’s done, but elves think that a landscape should look “natural”, and should have waterfalls, eroded mountains, and in general be smooth rather than square.
So maybe Neyd had a staff that could accelerate erosion and entropy in a given area. Stone-singers would create more mountain in a crude way, Neyd would make it look natural, everyone’s happy. Should your players ever find it and stick Neyd’s ruby in it, it could probably do a fair bit of damage to a castle like, say, Amber’s Peak or Vond.
The Mirror of the Ocean
This is a small green bronze mirror, the size of a tennis racquet. Rather than reflecting images, though, it shows you the sea; that’s because it’s actually a portal to somewhere on the continental shelf of Ravenland, a few hundred metres deep. Whoever owns it can eventually work out two ways of opening the portal: (1) gentle and (2) unsubtle.
In gentle mode, holding the mirror face upwards, you can force a lightweight object into the sea, or drop a heavier object onto it. The object will vanish into the sea and presumably be lost forever. Holding the mirror face downwards, a steady trickle of water will come from it. In unsubtle mode, water gushes from the mirror in great quantities, especially if it’s pointed downwards. Everyone agrees that the mirror was lost when its owner rashfully engaged unsubtle mode; scholars pinpoint a few so-called “naturally-occurrring” salt lakes as possible places to look.
Should your players ever find the Mirror of the Ocean, the constant source of water at pressure would be an excellent power source for a water mill, and could give you significant economic benefits. (And when you’re not using it, you can use it as like a water cannon against monsters.) Just take care about where the water goes, or your neighbouring farmers are going to start complaining that all of their crops have died of salt poisoning.
Also, it’s the exact same part of the ocean that stuff goes into and out of. Eventually someone might notice. Demons are experts at portals, and could probably eventually find their way through a portal that’s supposed to be one-way only.
Water-breathing devices
My headcanon is that the Shardmaiden had a number of elf followers who helped her sing, and when not doing that explored what it was like to live in the ocean. And in the same way that some elves these days decide to become trees and we call them ents, there are elves who have decided to become merfolk. They’ve built wondrous caverns underwater, and if you want to pay respect to them properly and learn from them, you need to breathe underwater. So at one point a bunch of water-breathing devices, maybe packed together in a small copper chest, just enough for a PC group, turned up as a gift from the sea.
Sacred tablets of Wyrm
Wyrm wrote down some commandments or tenets on metal plates shortly before journeying to Ravenland. These plates subsequently washed up, and were miraculously still legible (possibly because they were made of titanium inlaid with gold). That they were made of metal but didn’t rust was part of the original schism of the Rust Brothers, who rejected this impossible perfection as some kind of Elven / Elvenspring trickery.
Less consequential / more rubbish artifacts
It’s quite possible that most, if not all, gifts from the sea have in fact been manufactured by normal fleshy people, and then parlayed into importance by people agreeing that, yes, they’re so impressive that they must be of divine origin. The flip-side of this argument is that sometimes the artifacts were not, in fact, divine-looking.
So maybe a belt of the octopus, that gives you four extra limbs, but which you can’t control / are a bit flimsy and rubbish. Or a magic net which catches fish once per day, and then you need to revert to using your normal net.