After playing the Secret Wilds adventure, the pages drawn by a child depicts Briggsy's journey in an ancient temple, filled with skeletons, but also reveals a doodle of a gate, with multiple red eyes of a creature guarding something that could cure the Undead Curse she sought after.
My theory is that Briggsy found this secret deeper underground at the Shores of Gold, but couldn't acquire it due to the beast protecting it, fearing of what would happen if it got out, she destroyed the entrance we see on the island that we can't open, and might also explain why the Ancients surrounded the massive island in the Devil's Shroud (if they had some way of using the red mists to shield the Sea of Thieves from the outside world) before Rathbone set foot on its shores.
Could it be a Sea Serpent with three heads, almost like the Hydra of Greek myth? Or is it perhaps the Old Mother? The largest Kraken in the SoT Lore that was bound and chained by the Ancients and the Merfolk? Perhaps thats what Wanda wants, since she just arrived out of nowhere, suspiciously wanting to help us and Briggsy find the cure to the Skeleton Curse. But her true goal is wanting to control the mother of all Krakens to serve her and the Dark Brethren.
