Sometime ago, I was on my way to kill the boss Scarlett, and this happened to me: 5 Strange rats just spawned, 1 in the middle and 1 in each sqm from his side (North, East, South, West). Also, a type of ghost blinkered at the center. Just like the animation when you trigger the lantern of Feaster of Soul Quest.
Here you can see the only clip that I found on internet:
https://clips.twitch.tv/PunchyMuddyCardMVGame
When this happened to me, it was so fast, that I didn't reacted and they disappeared.
Last week, I was hunting at Cobra bastion, and the same thing happen again. But that time, I was fast. In a split second, I was able to drop my avalanche rune on them. And they're dead.
They aren't bestiary creatures, so they're like "summons" or "bosses". Also, after you kill them one time, they keep spawning close to you, each 2 or 3 mins, until you can not kill them.
If you're not fast enough, they will disappear and you'll take days, even months, to find them again.
What is the link between those spirits and these strange rats? Are they connected somehow with Gravedanger tombs ?
Strange rats are just summons from something stronger or they're the real threat, that try to trap you, so you will get killed by Cobras ?