4. Arkham City - Scarecrow's Boat
Conspicuously absent from the second installment of Warner Bros and Rocksteady's superlative-inspiring game franchise, the brilliant Dr. Jonathan Crane still has a presence throughout Arkham City, although not in the most obvious of ways. To discover a shipment of cockroaches (whose intentions are unclear) as well as a thug under the influence of Scarecrow's fear gas, you will need to find a small boat with no visible entrance... It's certainly not an easy find, but using the Cryptographer will unlock a secret panel allowing access to the boat, as shown above, which reveals its gruesome contents, implying that the good doctor has something big up his sleeve. Additionally, Scarecrow's mask can be found on top of scattered hay on a building in the industrial district. These inclusions are excellent pointers towards a next game, though that could well be later than initially intended with Warner Bros releasing Arkham Origins without Rocksteady's help - but hopefully, we will get to see a fourth game in the series that brings Scarecrow back in a big way. They also provide atmosphere to an already dark game with the hint of evil inhabiting the same area; in operation but invisible to the gamer.