Is there anything stopping hero's from leaving 1 hero behind at the entrance to stop OL from spawning large monsters there?

The spawn point always isnt the entrance. But, no, there is nothing from preventing the Heroes from blocking spawn points.

wootersl said:

Except that according to the rules, this is impossible. You cannot prevent reinforcements from coming onto the map.

Per the Quest guide, page 2, REINFORCEMENTS:

"If a reinforcing monster cannot be placed as indicated in this section because the tile is full, the monster is placed in the closest empty space(s) instead".

We actually had an encounter where the OL was reinforcing a 2x3 monster, and due to where our heroes and his monsters were located, the closest space was actually 13 squares away from the actual reinforcement tiles. Bad play on our part and good play on his.

I can't seem to find anything in the rulebook right now about how the OL brings new monsters onto the map. Perhaps I'm just blind, or perhaps it's not mentioned in the core rulebook because it's covered in the quest guide or something.

Anyway, given the way that large monsters move in 2e, I would be inclined to rule that they could come on occupying the single open space and move around the hero, as long as they can reach a place where they can legally stop movement. This is, of course, barring any explicit ruling (which I can't find right now) that would contradict this idea.

If the spawn area is blocked the monster is placed in the closest legal space, usually meaning they're even closer to where they need to go to, so it's not really a very good strategy. The same rules apply in other situations, such as reviving a hero when a monster or other hero is on top of their hero token.

Steve-O said:

That's because it's on the first page of the Quest book.