Lord Zardoz
Explorer
My advice then for killing PCs - use *lots* of monsters, a good mix of minions and standards, plus 1 or more controllers.
Lots of monsters are generally more deadly than higher-level monsters - this is different from prior editions, where offense went up faster than defense. In 4e, if the party are missing on a '15' they're likely to retreat. If they're ploughing through swathes of enemies they're much less likely to flee, but large numbers of same-level enemies can inflict lots of damage on them.
Secondly, use waves of monsters within the same encounter - the party will be out of position dealing with the first lot, when the second wave comes in. A few more minions don't make much difference, but the death mage controller in the second wave was really bad because it further disrupted the PCs.
One "trick" might be to have two waves of enemies. Say, the PCs enter a dungeon, and they fight their first enemies. One of them runs away, and alerts another group. The party can try to stop him. If they don't a second wave of enemies arrives in 3 rounds. If they do, a second wave of enemies arrives in 6 rounds (they still hear the noise, but it takes them longer to get what is going on and where they need to go.)
This way, you can reduce the impact of the very difficult encounter - staggering the enemies advance means effectively improving the action economy to the party's benefit. But at the same time, it makes it more important for the party to use their resources wisely, and they cannot benefit from some "tricks" - like using area effects to affect all enemies, while others become more effective - like powers with encounter long durations, sustainable powers, stances, rages.
Using enemies in waves is something I have already started doing with 4th Edition. It allows you to avoid the problems of tracking too many combatants on your turn, and it allows you to sustain pressure on your players. It will make the fight feel longer, but the payoff in terms of sustained pressure on the players, and to the perception of risk, is great.
Regarding advice to use Level X+3 encounters on a Level X party, I do have a few things I should point out. The WotC printed adventures really like using monsters of a higher level then the players. The increase in AC and attack bonus is like trying to ride a bicycle up a hill. For a small hill / small encounter, it works fine. But the longer the encounter goes, the harder it gets. I have had a Level X encounter against Level X players using Level X+3 monsters result in having the players miss very often while nearly always being hit. This will turn an encounter bad pretty fast if the encounter is scaled as being difficult for the players according to the encounter builder.
When you break an encounter up into waves, you want to be using monsters as close to the PC's level as possible. Higher level monsters will get too lethal later in the fight. Lower level monsters wont create enough pressure on the players unless you are hitting them en masse.
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