Still makes me laugh how obvious of a troll it was from the very beginning, but no matter what people will find a mystery to solve (even when there isn't really a mystery at all). This is almost *definitely* a reference to an earlier Fromsoftware game that literally nobody has heard of or played (including me) called "Shadow Tower Abyss". It was only ever released in Japan. It's basically a predecessor to the Souls games... well, at least until it gives you a bunch of machine guns and a rocket launcher.
Anyway, there's an Onyx pendant that has incredibly similar text ("Old-looking item with no obvious value"). Also, you can't drop items in that game so it just sits there forever in your inventory.
The speculations are awesome, especially “I’m willing to be my left but this chamber is the resting place of the firstborn” lol. DS3 obviously confirms the firstborn’s identity and Zillow confirmed that “sealed chamber” was originally going to be the path to the Kiln of the Flame, to be opened by Andre (seen in the Design Works art book too)
There is a statue of a woman and child within the painted world, it turns around to allow you to escape, Priscilla being a half dragon, could have a connection to gwyn, and explain why there's an order of painting guardians to protect her, despite her description as an abomination, which, is also how death the scaleless has been described, if I recall correctly.
“pleasant memories are crucial to survival on arduous journeys."
I believe the pendant to be representative of the dark souls experience explained by this item description. We all remember our first DS1 run and how arduous it was. Maybe we even quit before getting halfway through our first playthrough. Butttt for some reason we came back. And then… we got good. The realizations and breakthroughs rapidly increased. We then explored different builds and play styles resulting in the memories DS1 has provided to us still present today.
The pendant is an in-game manifestation of our perseverance and nostalgia that drove us to complete this game on the first playthrough, and why we still come back to it this day. More generally, the pendant is the dark souls experience incarnate. In a game of enormous weapons and powerful magic, the developers told us the most powerful weapon in the item description of a starting gift; perseverance and nostalgia. That’s all that’s needed to get you through Dark Souls.