This mod alters many sounds, adds new gore and death effects and adds several new gameplay elements to improve the immersive aspect of RO2 and RS, including new weapons, dynamic movement speed and configurable zoom options.
This is what RO2 should have been from the beginning, this is what RO1 fans expected from sequel and it's not like developer couln't do it, they could easily but chose not to.
IOM is more immersive, more tactical, way harder than vanilla and, of course, it added content developer promised but never delivered.
I wish we had it back in 2011, RO2 would be way more then it is now.