This article was first broadcast in Episode Four on 20th December, 2017.
Lennon: Hey Ryu, what’ve you got there?
Ryu: Oh this? It’s just a magic item I found in the Gnomish Workshop
Lennon: Looks like a santa hat. Hmm, let’s see the item card: Hat of the Killer DM. When equipping this hat, make a constitution saving throw (DC15). On a failed save, the wearer becomes the Killer DM for the remainder of the segment. You may repeat the saving throw once per round. This sounds cursed.
Ryu: I’m gonna put it on
Lennon: That doesn’t seem wise—ok, you did it anyway. Ok, make a constitution saving throw… a 3. Really?
Killer DM: Mwuahhahahaaa! Where is Ostron? He is late.
For our first bonus, we’ll look at one of the most common, the flat bonus: simply take your roll, and add a number to it, such as 1d8+2. Simple and straightforward, this bonus type is used throughout D&D, from attack rolls to skill checks, saving throws to damage modifiers. On the plus side, it raises the minimum, the maximum, and the average (aka the mean) of your roll. Whether your d20 rolled a 1, a 20, or somewhere in the middle, you’ll have a better roll with the flat bonus than without.
Killer DM: On the other hand, it doesn’t scale very well for larger rolls. When throwing 20d6 fireballs at your players, a +1 to the damage roll just doesn’t seem to be terribly thrilling.
For our second bonus, we offer the related but lesser-used per-die flat bonus. To use it, you add a number to each die rolled, rather than the total. D&D generally only uses this to represent multiple hits on a target, such as magic missile’s 1d4+1 per missile. Like the flat bonus, it raises the minimum, maximum, and mean, but it also scales with the number of dice. The more dice you can throw at it, the better the bonus gets.
Killer DM: And the fewer dice you roll, the worse it gets. I recall once giving a player a +1 per die bonus; he was so thrilled, until he realized he only got to roll one die.
For our third bonus, we’ll look at one which was introduced in 5th edition, rolling with advantage. When you have advantage on a roll, you roll two d20s and use whichever is higher. While D&D uses it only on d20 rolls where one party has a situational advantage over the other, there’s technically nothing that prevents it from being used with other dice sizes.
Advantage has an interesting effect on the roll; the minimum and maximum possible rolls remain the same, but the average is skewed higher. More interestingly, the impact of the bonus varies on the target number. On a roll of 1d20, if the target number is 10 or 11, advantage will make you 25% more likely to succeed, equivalent to a +5 to the roll; as the target gets closer to 1 or 20, the effectiveness of advantage diminishes. When used in a situation where there is no target number, such as rolling 1d8 damage, you’ll still tend to see higher numbers with advantage than without
Killer DM: On the other hand, because the maximum is not affected, sometimes no amount of advantage will save a player; they will never be able to roll 21 on 1d20, advantage or no. An excellent way to crush a player’s spirit in the face of imminent doom.
The fourth bonus type is a variant version of Advantage, known as the “add bonus dice, drop lowest” bonus. For example: taking a 3d6 roll, rolling 4d6, and dropping the lowest die. If this sounds familiar, it’s because this method has been in use since 1st edition to roll ability score. Unlike its cousin Advantage, though, this bonus is rarely used in this form during the game, but DMs could consider using it for some variety.
Like Advantage, the minimum and maximum rolls are the same, but the rolls will tend to be higher. Unlike Advantage, it can be used with more than one die, and in situations where there’re no target number.
Killer DM: I do not like this one; it lets players roll more dice, and even when they’re facing imminent defeat, rolling large numbers of dice makes them feel…happy.
The fifth bonus is yet another close relative to advantage: the “reroll below X” bonus, as used in 5th edition by the Great Weapon Fighting fighting style [sic]. With this, any dice below a certain value re-rolled; for example, roll 5d6, re-rolling any ones or twos. Like “roll extra, drop lowest”, the player rolls extra dice, but the number of dice will vary based on how abysmal the initial roll was. If you roll 5d6, re-roll 1s, you could end up with zero to five “extra” dice, depending on how many ones you rolled. Some versions of this bonus let you continue re-rolling any dice that roll below the indicated value, but 5th edition allows only a single re-roll.
If the player is only allowed to re-roll once, the effect is similar to Advantage and “bonus dice, drop lowest”; same minimum and maximum, less chance to roll low, greater chance to roll high. If the player is allowed to keep re-rolling dice that fall below the threshold, it has the added effect of raising the minimum value in addition to the mean, since no combinations that include the below-threshold numbers are allowed.
Killer DM: I prefer the variant that has them continually re-roll when the roll is above a certain value. I cannot let the players get too pampered, after all.
On the topic of re-rolls, our 6th bonus is another, more fickle bonus type that allows the roller to re-roll dice at their discretion and use the new value, such as when using the Halfling Luck ability or Empowered spells. While the player can choose which dice to re-roll, there’s no guarantee they will roll any better they already did, and, importantly, they have to take the new result. If they rolled a 15 and were hoping for a nat 20 but rolled a 1, then what would have been an acceptable hit is now an instant miss.
Again, the minimum and maximum rolls are unaffected, but because of the uncertainty of the re-roll, being too greedy can just as easily make the new total worse than the original…something of a booby prize of bonuses.
Killer DM: Yes, I do love watching players ruin themselves and save me the trouble of doing it for them.
To be continued…