If it were any other sacred-blood creature, Han Sen would not use the sacred-blood butterfly boomerang. After all, it would be a huge waste since no one could guarantee he would gain a beast soul from a creature.
However, the sacred-blood creature from the Mystery Island would definitely yield a beast soul. In addition, it also had a sacred-blood gear, which was way better than the golden axe of the bloody slayer, which was too heavy to carry around and less sharp.
Even he could not bring the sword out of God's sanctuary, he would be able to sell it at a great price.
If he could kill this creature, he could gain both a beast soul and a gear. So even if he were to use his sacred-blood butterfly boomerang, it would be a great deal.
Going back to the mountain, Han Sen saw the sacred-blood creature under the tree, its hands still on the hilt of the diamond sword and its eyes closed again.