Don't be hasty 2, Uncommon, 0-cost
If enemy has received more than one positive effect - randomly negate one of them
Unless this were coded very specifically to ignore standard production, this would always trigger except after a production x0 effect. Probably an easy fix, though.
Would +stock be treated as one effect or as three when negated? If as one, what about after a card that increases two resources like Hidden treasure? Would it then only negate one of the two resource gains? If someone triggered Alliance along with a gems production x2 effect, would it negate the 4x gems production to instead be x2 or x1 (or x0)? Right now, it's hard to figure how this card should behave.