Anyone notice a pattern on where these are spawning ?.

Maybe I should ask if you've even seen one.

I've only seen the Layton. Boss once myself between the Suanil battlefield and Trent. Just happened to be running from Keplan and Killed him only to roll a Cron stones.

Obviously that wasn't the higher tiered Desperate Dead box Boss such  as Skeleton. King 

What's been your experience ?.