I don't know if I posted about it before, but I have always wanted to run an adventure set in a library. The following is a sketch of an unusual premise and a possible plot-hook.

Language is an essential part of any culture. Culture wouldn't exist without some form of communication, and humans communicate by speaking. But the connection is deeper even than that. The language helps to define the culture which uses it, and is in turn affected by that culture. This dynamic process is what keeps a language 'alive': Latin is a dead language because the culture to which it belonged no longer exists.

In the darkness in the south transept of the Cathedral of Isielles stands the resplendent Clock of Shadows. It tells more than just the time of day...

An impressive citadel in the Askharnn mountains. Their prohibitive laws on travel during the Winter months can be a problem for pilgrims and wanderers.

An icky sideline plot to a forest adventure.

A dangerous book of maps...

The characters are stranded on an island, where a wizard, corrupted by the powers of the first Blue Book, has been killed by his own magical experiments. They will discover the awful truth that lurks in his subterranean workshop, and a seed of evil will be sown...

To give a world a feeling of otherworldliness, it is best to replace some standard, everyday objects by imaginitive replacements. I thought I'd turn to musical instruments as music often defines (or embodies) a culture.

This is just a first idea, feel free to post some more, because I will...

Two sly-looking men turn up in town accompanied by a third man who says very little and who they don't allow to be seen much.

She has everything: stunningly good looks, sharp brains and oodles of power: she's going to be a Queen. The only drawback is that she doesn't want to be a Queen.

Carmo keeps a shop in the backstreets of Erezi. It's not often visited, Carmo makes people feel...uneasy. Even the veterans of the Erezi underworld are uncomfortable being alone with Carmo. But they need to buy their traps from somewhere...

The silver necklaces whose inset gems display the status of the wearer.

The mystery of fyre is one which has much occupyed my studies and the studies of men before me. ... I have concluded that fyre is the product of Fyre Antes.

Professor J Klewlise, "On the nature and origin of fyre" (1542)

Hathalfar holds the writhing troll down with his gloved fist and sword. The beast squirms at the touch of metal. 'How far is Kolm?' he demands for the third time. 'I said! A long way away,' replies the troll.

A (fairly sketchy) outline of a one-off adventure I ran based around the (time-honoured/hackneyed) Tunguska Event of 1908. As such it is quite specific (hopefully not hackneyed) and will probably best serve as a specimen for dissection to get those parts you can use in your own adventures. But then this is an Ideas Guild after all...

The addition of “irrelevant” details adds local colour to a campaign world, giving the impression that the DM has thought very deeply about the history of even the smallest architectural feature.

A disembodied hand enthralled by an evil wizard to fetch books for him.

A mysterious quarry. Feel free to suggest explanations - it's just an eerie thought that struck me that I intend to play with.

Although it can be a distraction, it can also add atmosphere to an adventure to have music playing in the background. Here are some pieces I'd recommend for different situations.

The grisly anthropomorphisation of a rockfall...