Losing mana with basic atk ?

I'm a mage and my mana regen is at 1/5s

For some reason I lose mana quite fast while only using basic atk on mob without even getting hurt

I went to hunt some mob lvl 80 and after killed all of them just with basic atk my mana drop from 20 to 0

I also tried on mob lvl 7 and it did the samething ...

It never did something like that before today

 

Do you have negative mana steal?
If you do there's a chance for your main attacks to make you lose mana.

 

Oh indeed I have -3/3s mana steal but it never took my mana before anyway thx you

 

sometimes it might not be so noticeable but it exists there, so be aware of your mana stats

 

Currently on live servers mana steal has a % chance to trigger based on your attack speed, so it's possible you just got lucky and it never triggered before. (Or it did and you just didn't notice if you were also casting spells). Worth noting that mana steal and life steal will change to always be triggered in 2.0 at reduced values with faster attack speeds