please find a page in the new rules book for this
https://koboldpress.com/friday-funny-the-dead-template/
especially these parts:
In The Way — The Dead creature counts as difficult terrain for any creatures 1 or more size categories smaller than it.
Smells Awful — Dead bodies smell pretty bad. Keep track of how long the Dead creature has been dead. Use a d30 for random Dead bodies (probably needs use anyway). Fort DC 10+2+(# of days dead / 2). Additional dead bodies adds +2 each, or +3 if over 20 days dead each. Failure means the creature becomes sickened for d6 rounds. Failure by more than 5 means the creature is nauseated until 40ft from any Dead body or 2d4 minutes. Failure by 20 or more means they become panicking until they leave the dungeon or area they are in or 3d6 minutes later. Any character that fails by 5 or more takes the most severe penalty first, and then once thats resolved the next worst. For example, a character that fails by 20 will panic for 3d6 minutes then be nauseated for 2d4 minutes and then be sicked for d6 rounds.
No experience awarded for defeating however if a play says " Hes dead Jim." that play is awarded or penalized 5 role play xp depending on the GM's mood.