The challenge is called Vampire, which causes association blood.
There is also this gif in the website:


Those two made me imeddiatly think about heartbleed, also the website has a self signed certificate so it's also suspicious.
I have used metasploit to try and check if it's actually vulnerable to heartbleed and it is:

Now i can run the exploit script serveral times to leak some data:

Now the website had a login page, so i decided to grep the leaked data for username and got the flag:

Flag:
```
BSidesTLV2020{Bl00d_Bl00d_Bl00d!!!}
```