Skeleton Pile event in first level

[Abstract]

On second run, I was running around while the lich was out and came across a skull pile with a cross sticking out of it and a purple circle around it. Killing enemies reduced a number to zero, which eventually exploded into some sort of purple crystal that when picked up, moved next to my exp bar. I died shortly after and have not been able to find it since over several runs. Is there any indication in game as to how to find this again, and if not, how do I do so haha

[dingus]

blood trails on the floor
if you find a book on a pedestal there should be 2 trails leading out of it
do the killing in the circles for both skull piles and youll unlock a relic that does a lot of damage to the zone boss

[Wardog Bob]

Often times it's just north of the well or in the least you'll come across the blood trail.