SoD_SP plugin.

What specific changes from HD+ are you referring to (especially regarding RMG, and by the way, there's a typo there)?

RNG - Random Number Generator
RMG - Random Map Generator

RMG is a large set of functions for generating random maps.
RNG is, roughly speaking, a single function for generating a random number, but it is used constantly in the game in various cases, both for random maps and for fixed ones.