^I've never had the chance to acquire one yet, but it sounds like after you beat them, they might offer you the hidden ghost, instead of the main ghost, or maybe WITH the main ghost. No one really knows, but I'll let you know when I've had the chance.
I think the only people who have a shot at ghosts are those either obsessively playing the game so they aren't wasting time and use energy as soon as it's refilled, or those who pay for items to refill energy.
I've been offered several ghosts, all have required 200 talismans and I just today broke 100. I'm not saying these should just be handed to everyone going through the shrine, but maybe the talisman drop rate could be upped so we all have a decent shot at a 200 talisman daemon by the end?