I like trying to draw these kind of curses out for an arbitrary amount of time so that nobody is quite sure the real reason for the craziness. It could be perfectly reasonable that nobody had a clue that it was the torc that drove the king insane and so it was passed on to the heir and they had a repeat performance in crazy. In that case I would delay it awhile to again, make it possible that it was hereditary or something.
This is a good opportunity to use and abuse the net book of riddles too. Everybody loves a fun riddle, especially if you can tie it into your game. Go to Comment
Again how would this be used by the PC? Solving a riddle or puzzle via a role is no fun. I suppose you could have some weird riddling NPC or as you suggested some King cursed by this, but those wouldn't require an item this indepth.
I am very curious as to how you intend to incorporate this item into game play. Go to Comment
The Lost March is a large collection of elephant rafts. The lost march never reached its destination and instead was pulled out to sea. The elephants on the raft eventually starved to death, littering the large wooden carpet with their bones and bird picked hides. While sailors with an eye for gold can salvage the tusks of the bull elephant for a hefty price, the raft is haunted by the spectral ghosts of the pod of elephants and they appear after nightfall and attack and kill anyone trespassing on their raft