Designing attacks to be used against the player for a puzzle game is challenging to say the least. Players expect a certain level of predictability and it's difficult to come up with ways to push back against their progress without making it feel cheep. I've broken all of Scout's attacks into two categories: Disruptive and Preventative. Disruptive attacks have an immediate effect on the state of the chain being solved, such as swapping the place of two tiles in the chain. (Seen below) These have a high impact, so they're used sparingly to avoid player frustration. It can be fun to reign chaos for awhile, but used too often and they create irritation.
The second category of attacks are the Preventatives. These are designed to make you quickly rethink your strategy and flow on the fly without breaking the action. In this example, Scout is attacking a tile to switch the controls of a single tile. While this won't immediately break the part of the chain already solved by the player, it will cause a delay in your solution if it lands in the right place on the board with minimal effect to player moral. As you progress through the story of Chained, Scout's power only grows as he develops new attacks to slow you down and break your progress.