Your PCs have begun their march down the King's Road. They're headed for certain doom and they are well-aware that not all of them will return. Why not dial up the tension a bit with the addition of a dread omen or two?
The fantasy rpg genre is rife with potions - they are often a blase affair with a simple effect (and a description of their color as an afterthought). In today's workshop, I try to make things a bit more interesting.