Ok so it was testing the theory wether or not someone could live if they drank the blood right before they died, meaning that if it worked on daniel euntae could also live if they used that way.
I have a theory about this, like the chapter where Yohan feed his blood to another vampire who is in the verge of death died and when Hayan feed her blood to Daniel, he became a pureblood vampire animal. So I was thinking since Yohan is only a half-pureblood vampire, it kinda doesn't work? i think and Hayan still only testing this on a vampire animal so there's a big possibility she can save Euntae by giving him her blood like 30/70 but I still kinda not sure here since Yohan eat the heart of Hayan's father to be a half pureblood, so how does will it work if you gave a vampire a pureblood from also a pureblood? will it also die or it will gonna prolong the life or it will also gonna be a pureblood? I dunno if I explain this understandable but I gave all the points i wanted to share, I think? haha
Wait can someone explain why Hayan's blood working on Daniel means Euntae can be saved???