I'd thought I already posted this idea but I couldn't find where I had. Sorry if it is a duplicate.
New game ability: interrupt the game. It interrupts all ongoing abilities in the game and the last card played/used? by opponent.
Obviously a more powerful version of the traditional ITB. You could have a less powerful version that only interrupts cards not in battle. This meant to give a way to deal with a Unholy Writ etc. that was just used, in addition to interrupting sites, souls, etc.
How about an interrupt the battle and play a Dominant, card? Would that be overpowered?
Also I'd like to see some cards that target neutral cards.