Blood of Dawnwalker: What happens when 30 days expire?
The Blood of Dawnwalker makes it very clear at the start of the game that you are on the clock. Your family will be killed at Brencis' coronation in 30 days time, and everything you're doing as you explore the valley is in service of becoming strong enough to stop him before that day comes.
Still, that does beg the question: what happens if you fail? Does the game end? Do you continue despite your family being dead? Something else entirely? Well, wonder no longer, as we'll tell you exactly what happens and what changes when 30 days are up.
If you'd rather get everything done before that day comes though, check out our guide on essential quests before the 30 days are up for more information.
What happens when 30 days are up? – Blood of Dawnwalker

Source: Bandai Namco Entertainment
After 30 days are up, Brencis kills your family. It's really that simple. It's what he said he would do, and he does it. The game doesn't endthough, instead, you can continue playing for as long as you want, but rescuing your family is no longer your mission, it is simply seeking vengeance.
However, there is no longer any time pressure; you can while away the hours without a care in the world now that your main responsibility is out of the way. Of course, this will lock you out of the achievement you get for successfully saving your family, so if you do intend on letting the time limit expire, make sure you have a save file ready for when you want to go back and get it.
