Since I have a special interest in game balance and game design, I'm often interested in play testing and analyzing games. Now makes this especially interesting by being a full-featured tactical board game. Who needs role-playing, I'm just having fun fighting monsters!
I've done a number of fights against groups of monsters, now I'm looking at solo monsters. I have a group of 5 third level characters that me and my friend Erick constructed. First we fought the blue slime from the first module, using the same terrain. It is listed as a level 3 monster, and my numeric game balance calculations indicated that it is a level 3+ monster (on the high side of level 3). The fight ended up seeming appropriate for its level - it cost a fair amount of damage but basically we demolished the monster.
Then I had a fight against a black dragon. The terrain was favorable to the dragon: The characters had to fight on a 2 square wide path through the deep water of the swamp. The dragon is listed as level 4, but my calculations indicated it was level 6- (on the low side of level 6). Or rather, I calculated it was level 5- without the darkness ability, then I arbitrarily added one because the darkness ability looked scary but who knows how effective it would be. The players managed to squeak out a difficult victory, but then I realized I had totally forgotten about the dragon’s tail attack. I suspect it is quite possible the players would have lost the fight if I'd done it correctly.
The first thing I learned from the fight is a bit more about how lurkers work, and how the darkness field works in particular. The classic lurker is supposed to be a monster that spends much of the battle hiding, coming out periodically to launch a big attack. I've been very skeptical about this actually working very often in practice, because I know how difficult this is to achieve. Before playing a specter, I predicted that lurking would not prove practical, and I was correct. However, before playing the black dragon I looked at the darkness field and had a feeling that it could potentially prove very troublesome to the characters. As long as the dragon is sitting in his darkness field, there is very little the characters can actually do to the dragon. They cannot do anything to extinguish the darkness field, and they cannot enter the darkness field without giving the dragon a massive advantage. Blindly throwing ranged attacks at the dragon from outside the darkness field causes only a slight amount of damage, to the point that it seems like it might be very effective for the dragon to just sit in the darkness field until his powers recharge. And since the dragon is a solo monster, this doesn't hurt any of his nonexistent allies. So the dragon's lurker ability really works. The problem is, I'm not so sure it is entertaining to have a solo lurker. While the dragon is recharging, the characters are more or less waiting for the restart of the fight. Not very exciting. So I decided to have the dragon fight every turn and just use the darkness when it happened to recharge. This probably wasn't a great tactical idea for the dragon because it got terrible recharge rolls and was hammered while outside of the darkness.
So why did the dragon seem too powerful for the characters? The most straightforward reason was that it is a level 6 encounter. The DMG says such an encounter is a normal hard encounter. Maybe level +3 is just hard for higher-level characters, but for level 3 characters, this means the monster is about as powerful as the characters even if they have and use every daily power they have. Not very appropriate unless you want there to be a significant chance that the players are totally defeated. This is appropriate for comic books, but I don't think D&D is supposed to work this way. The monsters will just eat you.
One thing that makes a high-level fight like this even more difficult than it may initially appear is that the extreme toughness of the dragon dilutes the effectiveness of their encounter and daily powers. Even after you've used them all up, there is a lot of dragon to kill.
One thing I think is very interesting, though, is the idea that the tactical situation in D&D can be as important as the raw numbers. In particular, which side has the powers which totally hose the other side? For the party, it appears that the power which is really awesome effective is the fighter’s lockdown ability (combat superiority and combat challenge). The blue slime had no way to counter this power, so even though it did a fair amount of damage to the whole party, it basically felt helpless. It had no real tactical options, it had to just sit around getting beat on until it was dead. The black dragon, on the other hand, can counter this power. This left the warlock is the only character with powers that were especially effective against a solo monster. On paper, witchfire and dread star are unusually good against solo monsters. While this is true, the problem is that the only be used once each, and you are lucky if one of the 2 actually hits. While the monster is very annoyed for one round, there is no way you can even come close to killing a solo monster in one round. So when the next round comes, you are back to the same tactical situation you started with. This is totally different from fighter lockdown, which lasts every round for the entire fight - or black dragon darkness, which lasts as long as the dragon either lurks in the darkness or gets lucky with its recharge rolls.