>give my players a magical dagger-sized scabbard which can fit any sword (but only sword), no matter how big
>players visit a world which is an aftermath of a battle of enormous titans
>describe land and mountains cloved with swords that must be a mile long
>players know that titans' creations are all made of adamantine
>players go back to their home world after some adventures
>"I am a bit surprised you guys didn't go looking for a mile long adamantine sword to put into your scabbard."
That look of flabbergasted realization what a treasure they missed... pure gold