I am able to reproduce this at will. I recorded it in the video below. Basically if I put myself below 0 mana with sigil of hope I cannot use hammer throw even though I have Mana Starved Forging. Also if I try to throw a hammer and cast sigil of hope(instant node) at the same time while being at 0 mana it will put me at negative 300+ mana. The mana globe then has to “empty” multiple times before I can do anything.
