Lurker has a fun interaction with Castles, since Small Castle and Opulent Castle are both Action-Victory cards. You can play and trash your Small Castle to gain another Castle and then regain it with Lurker--just don't leave it in the trash too long or your opponent might nab it with their own Lurker!
Opulent Castle can also be trashed and gained with Lurker, which is helpful for getting it for the first time, and in rare cases can also make it a nice reusable target for TfB cards (TfB in general tends to make Lurker much stronger). For example, in a recent game, trashing Opulent Castle with Apprentice became my main source of draw (+7 cards!), and then I'd just make sure to pick it back up with Lurker to use again next turn.