Assistance with Brigadoon type adventure

[Pooh]

My players have been pretty much plowing through whatever monsters I put in their way so I'd like to throw a change up in their path with an encounter that involves little or no combat.

The party is currently in the wilds of the 5 Kings Mountains and will find a path that is only visible in the right moonlight. If they follow the path it will lead to the very old ruins of what was once a grand manor house in the middle of the forest.

A detect magic will reveal the whole house is infused with residual magic. The obvious way into the house is through the still intact front door. When the door closes, the ruins vanish and instead the PCs are in the manor at the height of its glory and an elaborate ball is in progress.

If they try to leave, they will see a very changed landscape. Instead of wild forest they will see farms and orchards in the moonlight. The guests will try strenously to prevent them from leaving.

They will be welcomed as additional guests and offered food and drink and can engage the others in conversation and dance with them.

The challenge will be to figure out what's going on and how to get back to where they started.

In fact those in the house are from the distance past. an unspeakable horror was engulfing their community and there was no way for them to stop it. A powerfull enchanter who could not bear to see his friends and neighbors suffer the horrible torment that awaited them, invited them all to a last ball then performed a spell that removed them from the material plane to a place where they will enjoy this ball forever.

I've a number of ideas but could use some help putting this together.

Pooh

[Bwang]

One ST:TNG episode I've only seen once had the village existing only as an uber-advanced hologram. Only 'grandfather' was real, everyone and everything else was energy constructs.

I did a variation ages back. The village was about to collapse into the sea and the party stormed into the town hall to rescue the residents. Long, complicated story short: Everyone had died ages before, but a Lich had been raised there, came back and 'saved' the villagers in the 'happiness' of a harvest festival from his childhood. The 'unspeakable horror' had already occurred. No one knew they were dead and the Lich had pumped all his power into the spells to keep everything up. Now he was the only child at the festival and everyone else was in the prime of 'life'. Yes, It was a HINT! As he is little more than a remnant of his former power, I had him 'unkillable', reforming within minutes and 'adored' by all the assembled folk.

With the current write ups for Liches', I would make this a shot at redemption for the Lich, with the freeing the population to their eternal rest yielding him his on salvation.