I did read your story and Ive been holding back myself on participating on this thread for months until at least I showed a bit of my guys xD even tho I havent explained much so far.
Lets say, if they were humans, Dan would have killed them instantly XDDDD
In their spirit state- they have some rules to follow about not hurting humans or interfering with them- they still could have had some difficultities if following these rules and would only have acommplished to stop him temporarily (or knocked him down) maybe until your antagonist find a definitive way to stop him.
Its a bit unfair since Dan is more physical/material and closeminded character and my trio have advantage over him since them being invisible to everyone unless they want to show themselves.
Having free rein to do whatever they want, even with losing their actual powers, they could really harm Dan spiritually, in fact Caelis would be the one doing it but not killing him. Dont mess with Caelis