So, it looks like Daemon Targaryen’s long holiday at Harrenhal did have meaning to it after all. In a showing twist in the House of the Dragon season 2 finale, the King consort finally saw a Game of Thrones-related vision that made him realize what path he must take. Warning, major spoilers for House of the Dragon season 2 episode 8 follow , so make sure you are all caught up before reading on.
Throughout pretty much the whole of season 2, Daemon has been absent from his wife and soon-to-be Queen Rhaenyra’s side and instead at Harrenhal chasing ghosts and causing havoc with the townspeople. But aside from making alliances and building an army, which, spoiler alert, he does manage to do, Daemon’s time at the spooky derelict castle also opened his eyes to his past ways and what party he must play to save The Realm from complete destruction. In the season finale, Daemon is woken up one night by Harrenhal resident Alys Rivers , who leads him outside into the Godswoods, which is essentially a courtyard with a tall bloody tree, telling him "There are omens here for those who seek them.
.. do you wish to learn what is given to you?" Daemon presses his hand against the bloody tree and suddenly starts to experience vivid hallucinations of starting with a blonde man with a bird-shaped birthmark.
A three-eyed raven then flies onto the screen, before we see The Ice King and his army march on snowy ground. Then Daemon witnesses a bloody and horrific war where many men and dragons lie.