that's not a weird question at all. But you're not talking about an engine, you just need an Artificial Intelligence algorithm. Try searching for "AI techniques" on google or something and you should come up with a lot of results.
The sad truth is, there IS NO copy and paste solution for AI, you have to build it from the ground up depending on what your game is like. So I'd suggest grabbing a book or 2 about AI in games (trust me, there's a lot). Most of them have simple solutions that provide way more information than you'll probably ever need, unless you're looking to design something revolutionary, which I kind of doubt.
PS: you don't have to put quotes around "engine" every time lol