Concept: All-minion combat
Tested in: The Great Tower of Oldechi
What it is: In D&D 4E, minions were a creature type with static damage and only one hit point. They rarely had more than two powers (a melee attack and a ranged attack, or an attack and a movement power, etc.) and almost never had any consumable power. They were intended to supplement an encounter and give the PCs some roadblocks on the way to the actual monsters, serving as fodder the party didn’t have to focus on but couldn’t ignore either.
The rules said that four minions equaled one normal monster for the purposes of the XP budget (though later rules suggested using five minions at mid-level and six at high-level, to account for their low damage growth and the PCs’ increased access to multi-target powers). Since 4E was based around five monsters per combat, that meant a combat with twenty minions was technically a fair encounter. I had a party exploring a coastline, so I decided to hit them with a horde of murlocs, the numerous, irritating creatures we all knew from World of Warcraft.
What I wanted: The PCs beat back an ever-increasing tide of murlocs, holding their position as they gradually get overwhelmed by the sheer mass of enemies.
How it went: When the battle started, the players started by picking the enemies off at range. Though they started the battle surrounded on all sides, they didn’t really care until the second and third wave hit, and even then they maintained full control. Half of the murlocs never made it to the party, falling to a ray of frost or a vicious mockery before they could close the gap. Eventually I did get several creatures into base contact with the party, but the players barely noticed. They didn’t view the murlocs as a threat, even when I got five or six attacks against them per turn. The damage just didn’t matter. All I really did was heavily restrict PC movement, and the players walked away virtually unscathed.
What I learned: An all-minion fight just isn’t interesting on the mechanics alone. I also have to make each enemy narratively threatening. If the players have to keep on the move, fending off murlocs who are trying to collapse a bridge or kill some NPCs or something, that gives the fight some element of tension. Since each monster is simple and weak, the sheer number of them must have an effect greater than guaranteed flanking. Ideally this effect would increase over time, so the party’s control over the fight steadily slips as it goes on, which means I either increase the monsters over time (boring) or give the monsters some milestones they can reach that give them an advantage, like creating a new spawn point or making some part of the battlefield inhospitable to PCs (much better).
Either way, I think this is a fine idea that I handled poorly, and I want to do it right next time. The party in Under the Stars is probably too low-level for a proper test. The party in Faith is not.