Ye Olde Inn

The threat of an occasional patrol can help add a bit of pressure, keep the heroes moving along, and generally add to the difficulty of a dungeon.
Create a shuffled pile of all the monster cards, placing them face-down behind the screen. At the begining of Zargon's turn, draw a card. If it doesn't match the wandering monster type for the dungeon, discard it. If the revealed card matches the wandering monster type for the dungeon, place a skull marker nearby and shuffle both the card and the discard pile back into the monster deck.
Next, roll a six-sided die. If the result is greater than the current number of skull markers placed by the monster deck, nothing happens. Should the die result be equal to or less than the number of skull markers currently placed by the pile, then remove the skull markers and place a patrol of that many monsters on the board.
They start together and out of line of sight, as close as possible to a hero. When possible, the patrol starts on an explored square, or an unexplored adjacent square if around a corner. Otherwise, the patrol waits on the other side of the next door that is opened.
A patrol is made up of the wandering monster type for the dungeon. However, more than one designated monster card can form a patrol, if desired. This will increase the frequency of patrols, as well as create mixed groups. Similarly, more than one designated monster card may add a patrol monster, but additional cards can work as proxies for the single, desired wandering monster type.

For an easier to manage patrol size that appears more quickly, roll two red dice. If either die is equal to or less than the number of skull markers currently placed by the pile, then a half-sized patrol is placed on the board (divide the higher-qualifying die by 2, rounding up).

great idea !

Thanks. I made the rule to combat players that over-optimize their play, which somewhat defeats the purpose of red movement dice and the point of a Search action. With unlimited turns, players tend to always group the Heroes together while exploring and over-search areas for traps, treasures, and secret doors. A penalty in wandering monsters appearing forces the players to make some tactical choices. Now, a player will have to weigh the value of discovering all potential traps or secret doors vs. avoiding monster patrols (the treasure deck already contains this element of risk). It also makes dungeon sense that the longer you putz around, the greater the likelihood you encounter organized opposition.
I don't get to play much, but the basic rule worked quickly enough. I still want to test the red dice option so as to see more immediate effect.

When we played Into the Sewers this weekend, I asked the Heroes to roll on a matrix each GM turn, when no monsters or events were taking place.
1-2 nothing
3-4 wandering Monster
5 Spear Trap
6 Pit Trap.
If a Trap or WM turned up, I had given each Hero a dice number, and asked one of them to roll on this matrix, then carried out the consequence as normal rules.
As has been said, there needs to be more uncertaincey in the game

Seems to be some confusion about this idea, we only used it when nothing was about to happen on the GM turn, ie; no monsters, no traps, no searches, no nothing, just the heroes move about to follow the heroes move.

I'm guessing there were a lot of rolls on the matrix. Do you remember approximately how many? How did the players respond to the added pressure?
Also, I'm not exactly clear on how you used it: If a wandering monster card was drawn from the treasure deck, did you roll on the matrix instead? Likewise, if a trap was marked on a square on the map, do you mean to say that you would change triggering the trap to a roll on the matrix?
What kind of trap did you use for a trap matrix result?
My confusion probably results from my limited familiarity with the European rules set.

That clears things up for me. I think selectively adding some pressure to certain Quests sounds cool. If there's enough going on to keep the entertainment value geared up, then an optional rule isn't really needed to cover for it. An experienced Morcar/Zargon with some game sense goes a long way. Having additional tools to do the job just helps Morcar/Zargon get things done in a better fasion.