"Neither steel nor stone could cause any damage, my Lord... It was simply too big, unlike any enemy we have ever seen."
Legion Captain Meron's last report to General Lorgar
"When the trees shuddered and the earth shook, we knew it was far too late to retreat."
Excerpt of General Lorgar's last report to Emperor Paulus, following the loss of his entire army of 10,000 men
When was the last time a character caught a cold or flu? Real people get them every now and again even with solid heating and dry interiors. Your characters are out in the cold and wet, and even inside is not always dry and warm. Imagine having to stop your dungeon crawl, sitting in a tight defensive position, while you all are feverish.