There are 16 Clockwork Castellans to find in total in Resident Evil 4 Remake. They are small doll figurines hidden in various places in the game that need to be destroyed. Most of them are very difficult to spot but somewhat helpful in finding them is that when you are near the Clockwork Castellan, you will be able to hear its distinctive ticking-like sound. To make it even easier, you can turn on the closed caption subtitles in the settings. With this option turned on, a caption displaying "[mechanical cadence]" will appear on your screen whenever you are in the vicinity of a Clockwork Castellan.
After destroying the first one you will receive the "Revolt Against the Revolting" achievement / trophy, and you need to find them all to get the "Revolution Wind-up" achievement / trophy and the Primal Knife.
Note: I've put in parentheses the earliest chapter in which you can get to a given figurine and destroy it.
ncG1vNJzZmifpZ6xpr%2BToJimnaKoe6S7zGipnquZmbKvwIyeraKkXWl6s7HMmqKeZ6CktnCvy6iapK%2Bfp7hur8Csq56knJa7tHs%3D