well, the very first link when i click that offers the patch for downlod, and inside that 1,4MB is a readme.txt

stuff like
- A note on diplomacy. The stronger you get, the more difficult it will be to maintain good diplomatic relations with the other wizards and the more likely they will be to delcare war on you. They will not allow you grow strong unchecked.

- Spell blast should now work properly against disjunction.

basically bugfixing and balance issues.

if you only know the original, unpatched MoM, then there are more differences, because with 1.2 (included in 1.3.1) they made many (though mainly minor) changes to spell-, building- and unit-abilities.


the game still crashes on me from time to time in Dosbox, but not often. once every 6-8 hours maybe.
edit: on a PC, that is...