A few years ago I read something about the value of always rolling for the hit points of creatures and NPCs that the players get to fight and not always taking the average by default. I really like the idea of using different hit points to give individual opponents a bit of a personalized description even though otherwise they have completely identical stats with the same AC, saving throws, hit chance, and damage on a hit. In a fight against some random orcs or bandits, it can be a neat and convenient inspiration to have those with 7 hp look much larger and more menacing and approach the fight different from their otherwise identical buddies with only 2 hp.
But sometimes, you might want to know what actual hit points numbers might be realistically expected for a given number of d8s. So I made this little table. The math magic behind calculating 2 standard deviations for normal distributions isn’t really important here. What this table shows is the range of hit points into which 96% of all random rolls will fall. There is only a 2% chance that a randomly rolled number will be lower than the shown range, and a 2% chance that a number will be greater. It will still happen occasionally, but even then most likely only by 1 or 2 points, and for the purposes of encounters in an RPG, I consider the odds negligible. You can just assume that pretty much all randomly rolled hit points on a d8 will fall into the shown ranges.
| Hit Dice | hit points |
|---|---|
| 1 HD | 1-8 |
| 2 HD | 3-15 |
| 3 HD | 6-21 |
| 4 HD | 9-27 |
| 5 HD | 12-33 |
| 6 HD | 16-38 |
| 7 HD | 19-44 |
| 8 HD | 23-49 |
| 9 HD | 27-54 |
| 10 HD | 31-60 |
| 11 HD | 34-65 |
| 12 HD | 38-70 |
| 13 HD | 42-75 |
| 14 HD | 46-80 |
| 15 HD | 50-85 |
| 16 HD | 54-90 |
| 17 HD | 58-95 |
| 18 HD | 62-100 |
| 19 HD | 65-105 |
| 20 HD | 70-111 |
My main argument against this is that it increases the amount of things I have to keep track of. I have to try and remember which of the guys I said was bigger or smaller, and therefore has more or less HP. I either have to roll stats before we play, or I have to grab a bunch of dice and roll HP stats at the start of combat.
I try and run combat with minimal information for myself to keep track of so I can focus on keeping track of other information. I really like the idea of using the exact same statblock to make something feel stronger than its peers, but I feel like it’s easier to trust my gut than to just use dice to create a bunch of extra arbitrary numbers to keep track of.
I’ve always loved the “Bloodied” mechanic from 4th edition, where you can almost explicitly tell the players that an enemy has been cut down to half HP. I feel like an easier way to get the effect you’re talking about is to roll one of your monster’s hit dice, or even just an ordinary d6 when they’d normally be bloodied, and if they roll over a certain number that you set, hold them back from being bloodied. Now you can describe how they seem to shrug off the attacks with more ease than their peers, how they stand taller and almost seem to loom over the PCs. They’re bleeding, sure… but they aren’t bloodied.
Now you can mark one specific monster for the honour of being bigger and better. And maybe if they push back on the attack of being bloodied, you give them an increased chance of withstanding an attack when they’d normally be killed, as well. They hold on just that second longer in the fight. And this is something you can decide depending on the flow of combat and how deadly you want a specific combat to be. It’s something I feel gives you greater control, and doesn’t lock you into listening to the numbers over the fiction.