I think it depends on who reacts first, at least that is the way I play it. If you put down the dominant first, then his Herod's Treachery wouln't work before your dominant. If he discards Herod's Treachery first, then you can't play your dominant. Herod's Treachery is an ongoing special ability that has an ongoing effect unlike character special abilities that have to be worked out first before any enhancement/dominant is played. I do believe the card says, "...at any time during battle, you may discard this card to force X heros back to their territory."