There are very few engines on the Amiga because most developers found writing OS-friendly code to be a disaster of bad performance. As for the Metro Siege game, the tools used for it include Spriter beta, a Windows program for making modular animation, and ProMotion by Cosmigo (also Windows-only).
If you are looking for tools that actually can work on an actual Amiga, there is an engine with a graphical scripting language called
RedPill.
