Found this info in issue 164 of Compute! magazine:
"The news hasn't been good for what looked like a promising entry in the Ultima Underworld school of free-scrolling RPGs. Twin Dolphin Games' Forgotten Castles, which looked dazzling at its unveiling at last summer's CES, has run into the computer-game equivalent of the tuna net. The EA affiliate was to have delivered the game last November, but delays in finishing the 3-D engine and interface ultimately led to the withdrawal of the company's main investor in late October. Matters were further complicated by the departure of the game's chief engineer in early December, according to president Steve Ruszak. Twin Dolphin Games itself probably won't last beyond the summer, but there are other fish in the sea, and Ruszak reckons Forgotten Castles--which is 60 to 70 percent complete--may yet surface. Both it and the 3- D engine are for sale as a package, and he's optimistic the company will find a buyer."
They got too ambitious, couldn't finish in time, lost support and died. Wonder if anyone bought the engine and used it?