In game I'm currently working on (which is a fully cooperative fantasy adventure game) there's a 'bad stuff' deck that has cards come out of it face down and move along a track, giving players an opportunity to deal with those things by seeking them out before they appear and cause mayhem.
In the deck of 60 cards, there are 6 cards that are 'Lieutenant' cards. These Lieutenants will be somewhat more dangerous than the other cards in the deck. The first two of these cards that appear will determine what enemy is the 'Overlord' for that particular game session and trigger them to then appear and cause even more mayhem.
The thing is, I'm trying to figure out a way to make sure that these cards don't show up either too early or too late. Being a fantasy adventure game there are aspects of leveling and gearing up that take place throughout the game. If the Overlord shows up too early they could have no hope of winning due to the combination of multiple Lieutenants and the Overlord being there before the players are ready. On the flip side, if they show up too late, the players could be left waiting as well as possibly becoming too powerful (though being too powerful might not be too much of a bad thing in this kind of game).
The options I've come up with.
A) Go Pandemic style and split the deck into multiple piles and place one Lieutenant randomly into each pile. This is the best option I've come up with as it keeps the appearance of Lieutenants balanced but also somewhat random. It does feel a little bit clunky in the setup, however. It also eliminates the option of shuffling other cards back into the deck, a mechanic I'm currently using on a few cards, but isn't a core mechanic and could probably be worked around if necessary.
B) The Lieutenants could not be part of the deck but a separate pile and could be brought into the game via game turn or some other mechanic. This makes it less mysterious as to when the Lieutenants appear and feels somewhat more gimmicky to me, but does allow for more control of the pace of the game.
C) Have the Lieutenants shuffled in the deck but have some mechanic that causes them to go away if they appear too early or be summoned if they don't appear soon enough. This is probably my least favorite of these options as it requires more clunky rules that could easily be confusing and mess with the pacing of the game.
I'd love feedback on those or any other ideas your brilliant minds might be able to offer me.
So, I already have a mechanic 'Chaos' which increases the number of cards being drawn from the deck each round. It currently increases in a few different ways.
-Start of the game to balance the number of players
-Certain cards if they are dealt with before they reach the end of the track
-Players 'die' (consequence instead of player elimination or going back to level 1)
-Parts of the kingdom are destroyed (villages & bridges)
I could directly tie Lieutenants to this Chaos track as well, which seems like a really smooth and natural implementation of your suggestion into already existing mechanics.
However, if the players were doing well they could end up in a situation where they wanted to game the mechanics and let the Chaos increase just to get a Lieutenant out, which I wouldn't want. This might be avoidable just by good balancing, though?