This definitely seems like a  bug, moved to bug reports section

Do you have any clue what causes that or are you able to reproduce it?

This definitely seems like a  bug, moved to bug reports section

Do you have any clue what causes that or are you able to reproduce it?

I've got no clue, i just decided to risk and try to finish it off, i had 19HP that time, it hitted me 19 the same i hitted him the final hit that killed him, the monster died but i were still alive and were able to teleport away.

Do you remember what happened when you relogged or ate another manta after ending up in that bugged, immortal state? Did eating a manta heal you for more than 23? Have you died afterwards?

Do you remember what happened when you relogged or ate another manta after ending up in that bugged, immortal state? Did eating a manta heal you for more than 23? Have you died afterwards?

After that i teled away to al kharid and got me healed up by healer. I didn't die nor lost my guardian angel.