Crown of thorns killed my character when entering boss room

Hello
I encountered a bug in which my character died as soon as I crossed the threshold of the boss arena Viper Napuatzi.

Afterwards, I found out on the standard that the crown of thorns was to blame because without it the character does not die upon entering

I am attaching a video

https://drive.google.com/file/d/1q2Ze6TCcQ5V_uuz3oHN0i6CP2IBip3Ts/view?usp=drive_link

Tell me why I died? Is it a bug or not? Now I'm scared to take a talent for 1 hp.

I'm not asking to return the character because he would have died anyway when using any skill, but I need to understand how to avoid such situations in the future.

The Chaos Inocculation passive node and Crown of Thorns unique helm interaction is not a bug.

I understand that. But I have a different problem. I didn't use any skills. I crossed the threshold of the boss room and died in a way that I don't understand. And I consider this moment a bug.

I did another test and found out that when entering the boss room with the crown equipped, 5 hp is removed as if I used some skill. without the crown, hp is not taken away.

video with the test:
https://drive.google.com/file/d/1MJRQwdYeVEQyD3n4Hk20XcPSE9S7HECy/view?usp=drive_link