Every time I'm killing a rift guardian on a regular rift, it's dropping a glowing purple item that looks like I should be able to pick it up.
But when I try to pick it up, it says "My pack is full" or "I don't have a place to put that item." Even though my pack definitely isn't full. What is this thing and why can't I pick it up?
Blood shards.
It is bullshit, that you cannot get them to auto-stack to their limit of 500.