What if the Wyrdkeys weren't the only ones? I mean yes, in Erilea were the three keys for the three Valg kings, but what if in each world there was a similar thing?
In Cc we have the Luna's Horn that has similar powers to the keys, controlling the Northern Rift (coincidentally all the gates are in the north: Orynth; when Aelin forged the Lock, the Northern Rift of Midgard, and Aelin fell in the Night Court, also the north of Prythian), and it seems that what Danika did by tattooing Bryce the Luna's Horn on the skin, could be a kind of Lock like the one Aelin forged (similar at least).
And in Acotar, we have a magical object of great power, hidden on a secret island in a rough sea (the aquatic reflection of the Mala's temple in Volcano Flows) capable of bringing people to life and making them immortal, and it is the object that Drakon used to revive Myriam when she was killed by the Queen of the Black Land, sounds similar to what they said in Tog, that if Erawan had the three keys he would not need living bodies to implant the Valg in them, only bodies; and here is present an object that has already restored someone's life; the legend says that the Cauldron forged that object, but we already know what the legends are like; a little truth, a little lie and many things omitted.
Or it could even be the Cauldron (it seems made of Wyrdstone), but honestly it seems too heavy to carry in the pocket, and it also looks more like a contained portal or contained Wyrd; Nehemia explained: that the Wyrd was a force between worlds, what united things, not only symbols, portals and keys (something like that), as a superior magic, and the Cauldron is that, a magic well contained within, that if is destroyed, the world can no longer exist.
And even, the black stone box that Elain saw in one of her first visions, which belonged to a Lord of Death (surely Koschei) and which was his most precious treasure, we all know what the expression of black stone usually refers to. Or the black stone at the top of Ramiel that the elements do not touch and gives off an ancient power.
In Acotar we really have several options: the Cauldron, the object that revived Myriam, the black stone box that Elain saw and the black stone of Ramiel (three out of four are made of black stone, it cannot be a coincidence).
And then, there is the fact that are things from the three worlds intermingled, in Tog they give us the first clues and then they develop in the others, for example, the symbol of the Eye of Elena / witches / Three-Face Goddess, coincidentally it is very similar to the symbol that the Bone Carver draws on the ground when Feyre and Cassian go to talk with him and he tells about his brothers, and when Amren brings the bones and stones to Nesta to find the Cauldron, she says that the three stones are for the three faces of the goddess, then a book in Cc with the name "Queen with many faces" (it sounds like the Three-Face Goddess and also the witches of Cc worship that goddess), "The Walking Dead" (book about Wyrdmarks and portals) that we know tends to appear where he wants, and "The Book of Breathings" (book with a strange and ancient languaje) that Feyre threw into the remains of the Cauldron when it was destroyed, and may have fallen to Midgard perfectly through the magic of the wyrd inside the Cauldron ( a portal in this case), then it would not be strange to think that each world has its ways of controlling the portals and the Wyrd by means of "Wyrdkeys".
