I got one from the very first wraith kill. very lucky. Drauger elite and rancid remains were very elusive for me tho

Congrats on your trophy!

5% chance i believe, plus they are pretty uncommon. First game took me over 400 hours and easily over a hundred wraiths to get one. In my current game i got 3 trophies from the first 3 wraiths i found. At least you can farm them somewhat, the rancid remains trophy is my nemesis.

Rancid remains... not sure if I have that or not. I will have to look!

I've only seen the rancid skeletons in raids. Kill it quick to spawn another one.
Maybe saw one in a burial chamber once.