One of my favourite things about combat in D&D 4E is the existence of minion monsters. These little guys add a new dimension to encounter composition: we are no longer constrained to skirmishes between roughly equivalent groups, or straightforward boss fights. Rather, we can have the PCs face dozens of foes at a time, in battles of epic (though not necessarily Epic) scale. However, as much as I like the basic concept of minions, I can’t help but notice that their implementation doesn’t get everything right.
The bottom line is that minions are not threatening, as monsters. It’s not just a matter of XP cost: more often than not, adding more of them to a fight only causes them to die in droves after managing to make just one attack (if any), unless you are fighting in huge open spaces, and the minions in question have ranged attacks. Recent monster design technology tries to mitigate this with tricks like death triggers, which are nice enough, but ultimately, the only reliable way to have minions impacting a fight past turn three is to have them enter the fight past turn three. In fact, I have found relative success with staged groups of minions in my encounters. Also, you can just add one or two minions to an otherwise normal fight in the hopes that they escape PC attention long enough to survive the dreaded first rounds - I have found that this often works. Nevertheless, the problem remains that you can’t just have a group of minions make up a significant part of an encounter, and expect it to work. This needs to change.
After a lot of trial and error, I came up with the following house rule, which has addressed most problems with minions in my games:
Whenever a minion takes damage that is not the result of a hitting attack, if it is not prone, it can make a saving throw. If the saving throw succeeds, the minion is knocked prone and the damage is negated.
What does this do? The rule is intended to tone down the most egregious minion-wiping methods, without rendering them completely useless, while leaving fair minion-killing powers intact. That is to say, it gives a minion a chance to survive a Rain of Steel, Flurry of Blows, or pre-errata Flaming Sphere, to name some of the most common examples, but doesn’t stop tamer stuff like Cleave. Autodamage remains a very useful tool against minions, since it still provides a 45% chance of killing, and 55% of proning - and multiple instances should kill just fine, as prone minions can’t benefit from the save. Missed attacks are unaffected, since they still deal no damage to minions.
Applying this rule in my Trollhaunt campaign took some time to get used to (particularly for the monk player), but I can say that it had quite a positive effect in many minion-heavy encounters. Attacks that would have single-handedly destroyed the enemy hordes now left a few survivors to counterattack. A few heroic minions were even able to survive until the later stages of an encounter, more of an annoyance than a threat, but one that contributed to make the fight more exciting - we even joked about promoting a particularly persistent troglodyte minion soldier to standard status, after its prolonged combat experience.
As far as I can tell, this rule only negatively affects attacks that were on the abusive side against minions, with one remarkable exception: the Wizard’s Magic Missile. This power has already suffered enough from errata, and is the perfect attack to allow guaranteed minion slaying, so I would add the following line to it:
“Special: Any minion targeted by this attack is automatically reduced to 0 hit points”.