Played on top of the MM8 "shell" (ie uses the skill and spell system from MM8 - which is the same as MM7 anyway, but different to MM6), you can choose to start in any of the three worlds, and all races from all three games are available, although you can only start with the Classes from your starting world (plus Peasant). Eg if you start in MM6, which originally only had humans, you can have a Dwarf or Goblin or Vampire or Dark Elf or Troll etc, along with any of those race-specific skills from MM8, but you can only choose from the Classes available in MM6. The "monster" races were effectively their own "Class" in MM8, but the Merge Mod allows some interesting combinations like a Vampire Cleric, Dark Elf Archer, Minotaur Monk etc.

Once you start, you can jump between worlds as soon as you are able, and complete any quest from any game at any time, so the Merge Mod is essentially a big combination of all three games in a single playthrough with a single party, which is a dream for many of us old hands! There's also an option to buff the monsters which helps to stave off boredom because your party will eventually get to the point where you can easily blow through even the toughest monsters in "vanilla".

Which brings me to my actual question! One of the things that happens is your stats get huge, with all items, barrels, wells, shrines, potions etc from all three games, not to mention map resets allowing you to repeat. I remember there was a point where stats "wraparound" and if the value is high enough, it essentially drops back to 1 and gives the corresponding penalty, rather than a bonus. I know the highest Attribute bonus is at 500, after which there is no further benefit, but does anyone remember the value at which it wraps around and becomes worse?