Used
- Putting the players in an area with an invisible attacker who becomes visible when the players hit him. The players can always tell what side he's on when they take damage. If he is hit, his square becomes a sight square, and anyone standing in it can always see him. He moves in a pattern, attacking each player via teleportation, and the sight squares refresh once, forcing them to keep the pattern in mind. (I had an assassin teleporting in a fog of blood, with an illusory double just for kicks)
- Players must kill all the minions that a mob boss drops before dealing damage to it, and the mob boss adds minions each turn (I had diminishing numbers 8, 4, 2, then 1).
- Players have to take out a given number of points (I had 36 chains to be broken that held the MacGuffin) while one or more of the players discovers important things about the plot, and simultaneously needs to save against a continuously increasing DC (I had Fort starting at DC 1).
- Players have to guard a macguffin that either is inactive, beneficial, or detrimental based on a pattern of 5 which they get to glimpse sometime earlier in the story (N,B,G,N,G was my plan)