that appears to be modified sdeggs.cs that I also did not write.
Anyway I use them in a closed off location like an unused dungeon for new players to learn skills and choose their opponents and how many opponents they wish to fight. I do this because once spawned they are not attached to a spawner and will wander the world. So i put them in a small training dungeon and set movable false. I would really not reccomend using the one for the primeval lich as on death it rains gold and is messy to clean up.
Depending on your era some may need to be removed like trex, but the basic ones like mongbat, dragon, lich ect.. should be fine.