Everyone ends up with them. I got mine at a garage sale - I didn't look carefully as I snatched up a big bag of grey plates. However, they were perfect for making the slag heaps in front of the Gates of Mordor (79007 Battle at the Black Gate.)
"The gasping pools were choked with ash and crawling muds, sickly white and grey, as if the mountains had vomited the filth of their entrails upon the lands about."
"The gasping pools were choked with ash and crawling muds, sickly white and grey, as if the mountains had vomited the filth of their entrails upon the lands about."