Negative mana regeneration

Hello!

The question is quite simple: is there any way to have negative mana regeneration? From what I see, Broken Crown gives 20% reduction, Timeclasp gives 15% reduction, so we can have 50% reduction in total. Am I missing something, or there is no way to go to the negative values? Maybe some tricky mechanics?

Also, there is Shavronne Revelation, but it is, well, little expensive.

P.S. Yes, I'm looking for some ways to use anti-curse mana flasks with Soul Mantle.

Even if you could somehow manage 200% reduced mana regeneration, it would probably bottom out at zero and not actually go negative.

Can't you just use like Quicksilver Flask of Warding ? Even if it takes a bit more charges than Mana pots, the strugle to gen minus mana regen would be much more harsh.

Go back in time and use old Arctic Armour.