Help me torment my players

[Virfortis]

I want to make a fey-ish room with a DC16 Wisdom saving throw or the target is charmed and must start dancing around a central brazier while singing "The song that doesn't end (Lamb Chop Show, look it up)."
They join 3 other NPCs that are on the brink of exhaustion and near death, with skeletons around them of those that went in and failed.

However, giving them a save every 6 seconds would defeat the point/story, so I'm thinking dominate may be better. What are your thoughts? I'm ok with this being a relic because they could not feasibly disspell it long enough to matter and it would be always on, making it useless for their abuse.

Yes I will expect them to sing along as their character would.

[MrFahrenheit]

Rather than a wis save permitted every six seconds, it's a wis save every hour? To balance this (but barely), the characters don't have to dance in place, but rather dance around the relic? The relic itself would of course be a ball made out of multiple small pieces of glass, suspended from the ceiling by a wire - Otto's Irresistable Disco Ball hanging above Otto's Irresistable Dance Floor!

[Virfortis]

Rather than a wis save permitted every six seconds, it's a wis save every hour? To balance this (but barely), the characters don't have to dance in place, but rather dance around the relic? The relic itself would of course be a ball made out of multiple small pieces of glass, suspended from the ceiling by a wire - Otto's Irresistable Disco Ball hanging above Otto's Irresistable Dance Floor!

With blood on the dance floor, of course.

I like it.

[Sir cryosin]

Didn't critical role do this?