Upon entering the second holy mountain in a run, the game freezes. The log says that the "mtrs_sand_radioactive" material from this mod doesn't exist (or isn't found).

Entering the material file finds that the radioactive sand is mistakenly refererred to as "mtrs_toxic_sand" instead of "mtrs_sand_radioactive", which is probably what causes the issue, since a Reaction later in its entry refers to it as "mtrs_sand_radioactive" instead of "mtrs_toxic_sand".