Gameplay example:

Sir Nocturne leaned over the table and studied the map. In order to set up the "dark fog" experiment, he would need a dry location where fog did not normally form, but where lots of water could still be found. That meant a desert with a high water table. There were a few places like that, but the one that stood out to him was the Valley of Kings. The already eerie atmosphere would be a bonus. He grinned, feeling rather clever, and declared, "Let's go to the Valley of Kings!"

Astran folded his arms and squinted. "You sure about this? If anyone's testing out necromancy, we'll be smack in the middle of a zombie apocalypse."
"It'll be fine, trust me!"

It wasn't fine. By the time Nocturne had calculated the dew point and worked out the visualization of the spell, they'd run for hours from the hordes of skeletons patrolling the valley.

"Cruddy pieces of-" Astran spat as he bandaged his arm. "Good thing they were just skeletons instead of zombies. Are you sure we still need to be here?"
"Yeah, I'm almost done," pleaded Nocturne. Everything was ready. Water would be drawn up from the underground wells, and sunlight would be bent away from the fog zone. Energy would be leeched from the air and used to evaporate the water. If all went well, the evaporated water would re-condense into fog.

Holding this image in his mind and referencing the calculations in his tome, Nocturne began to concentrate.

Water bubbled up from the earth. The sky grew darker, and soon even the noon-day sun seemed little more than a strange sunset. With a hiss, the moisture burst into cloud. Fog fell over the valley.

"Yes!" Nocturne held up his hand to hi-five his partner.
Astran just folded his arms.

"Yeah, let's just get out of here now."