You need the Blessed Gourd to retrieve Spirits. An npc gives it to you early on. Fast travel to Bamboo grove - Snake Trail. As you arrive go to your Right up the stairs and thats where you find the npc. The spirits that you have fought and cleared along the way already will show on your menu in the keepers shrine, simply select "retrieve spirits".
I keep upgrading the wandering wight. I wonder if there's any other ones that are better. I think I have seven at this point. I'm only on chapter 2. I've got electric boss. The rock boss and the tiger Boss to beat. Having issues with all three.
I’m still using the wondering wight too, i think I’m at about 10 spirits now and so far I still like the wondering wight from its passive ability that improves your defense by 26. Also nice on how far you have progressed. The tiger boss has been one of the hardest bosses for me so far.