In this quest (quest #4 in the core game), the heroes need to carry a princess around the dungeon. In the rules, it states that:

"A hero can carry her without using his hands, but the hero receives one fewer movement point at the start of his turn (minimum 0)"

Our OL seems to think this should be cumulative each turn a hero carrys her. So one less movment point the first turn, two the second, three the third, ect. He says it signifies that the hero is getting tired.

I gues that makes sense, but i do not see anything in the text that says it increases by one point every turn.

Also, the term 'movement point' is different than 'speed'. So if a character with a speed of 4 does an advance action, he only gets 3 movementpoints if he is holding the princess. But a run action would give him 7 movement points.... right?

I haven't played that Quest in a while, but that sound absolutely insane to me.

Antistone is extremely knowledgable when it comes to the base game Quests, so hopefully he'll chime in. That being said, I think your OL is absolutely wrong about that otherwise the Quest guide would actually say that.

His argument is purely thematic and those rarely work in Descent. You could easily counter it with that these are mighty Heroes of old and they aren't going to get tired carrying a 90-120lbs kids around a dungeon for a few turns.

As to the second part, yes I do believe that if he delcared a Run with the princess in hand he would get 7 MPs.

I misinterpreted the sentence in the German version the same way. After reading the English text it´s pretty clear (at least to me) that it is not cumulative.

We tried the quest about four times. Three times with the "wrongly" interpreted rule, hero blunder. Fourth time with the easier interpretation - hero victory.

One of my players still keeps saying at the beginning of almost every quest that he won´t play anything where he has to rescue a princess

i am 100 % sure it does not acumulate... and yes if u run u get 7 movement points

Definitely not cumulative. There's nothing in the text to suggest that penalties accumulate, and there's definitely nothing that says how to cancel or reset them, so I don't even know how you'd finish the quest under that interpretation without making up additional rules.

And yes, movement points are different from speed; a hero carrying the princess that declares a run gets twice his speed minus one, and a hero with the princess and the Ring of Quickness that declares a battle gets no movement points (zero plus one minus one).

If this is the case would a hero who as battled have to spend 2 fatigue to gain one MP since after spending the first fatigue to gain a MP it would immediately be lost because of the princess?

No, because the loss due to the princess takes place before you get a chance to spend fatigue, and the quest specifically say sthere's a minimum of zero MP.

Ok that makes sense.