Bug or Mechanic? Skills Consume Life Instead of Mana

I’ve encountered a strange issue: all skills that require mana now also consume the same amount of life. For example, I have a skill that normally costs 190 mana, but for me, it consumes both 190 mana and 190 life. When I hover over the skill, the tooltip displays both mana and life consumption.

What I have checked:

All items in my inventory – none of them have an effect that could cause this.
Passive skills – I don’t have any that would explain this behavior.
No debuffs are present.
I switched to another act (Act 1) – the issue persists.
I’m playing as a Witch (Blood Mage), level 44. I first noticed this issue in Act 3, in the "Flooded Garden" area.

Is this a feature of a specific passive skill or an unseen effect, or have I reached a part of the campaign where a temporary mechanic is applied? Any help would be greatly appreciated!