Now we are making a card that brings pain, but not destruction to those decks.
I don't want to kill trifle and hand contract and maleficia/striga mechanic with one event card.
Similarly, Aye and Orun are both Trifles, and I wouldn't really want to discourage being able to play multiple of those in master phases.
If particular master cards - or particular "types" of master cards with particular mechanics - are the problem, I'd prefer to see counters that interacted more squarely with those mechanics. The collateral damage here to uncontroversial master cards seems much, much too high.
For example, if it's pool gain (particularly Villein) and blood gain (Giant's Blood) that are the issues, you might instead go for something like:
Impending Masquerade Breach
Event. Government.
Put this card in play with X breach counters, where X is the number of Methuselahs in the game. During master phases, if a Methuselah uses a single card or effect to move more than two blood from a vampire to her pool or from the blood bank to one of her vampires, turn that vampire and any cards on him face down, out of play (breaking any temporary control effects) until the end of the current turn, and remove a breach counter from this card. Burn this card when it has zero breach counters (but any vampires remain out of play until the end of the current turn as normal).
(The out-of-play text is based on Descent into Darkness.)
Hits Giant's Blood. Hitss Villein. Hits Minion Tap. Doesn't hit Grooming the Protege. Doesn't hit multiple Blood Dolls (separate effects). Doesn't hit Vessel (wrong phase). Doesn't hit Renewed Vigor (untap phase). Doesn't hit Concert Tour (untap phase). Doesn't hit multiple Life in the City. Doesn't hit multiple Hunting Grounds. Doesn't hit Striga or Aye.
The power level could, of course, be adjusted.
New Card: Reversal of Hierachy
