In this article I’m going to talk about adding class levels to a monster. The Dungeon Master’s Guide has some basic rules for doing this on page 283 but they don’t go into too much detail, and you’re on your own from there because you could end up making a CR 2 monster into a CR 13 or you may not change its challenge rating at all. I’m going to demonstrate how to do this with an example. I recommend using two tools, Monster Maker which you can download here, and the Quick Monster CR Calculator available here. Both of these tools make it easier to create custom monsters but you’ll still need to be familiar with how to calculate CR, since the CR Calculator will require you to input adjusted hp and AC and not the base numbers for an accurate challenge rating.
Creating the Hill Giant Berserker. For the first monster, we’re going to add four levels of barbarian (Path of the Berserker) to a hill giant. I’ll be using Monster Manual page 155 and Player’s Handbook pages 47-49. Many things will be staying the same as the MM but we will be changing some ability scores so some of the MM entry numbers might change. One of the good things about Monster Maker is that it calculates bonuses automatically based off of the creature’s ability scores and Challenge Rating (which you have to guess at first), so as long as you set these early on there shouldn’t be any wrong numbers in the stat block left over from the old creature. I’m not a big fan of just writing changes down and running off the MM stat block if I customize something unless it doesn’t affect CR or ability scores at all. Now, the more you do this the better you’ll get at guessing the final CR or hitting a target CR you have in mind. For now I’m going to assume a proficiency of +4 which means a CR of 9-13. I’m going to pick CR 10 to start with but we’ll most likely change it later, though with any luck, the proficiency bonus won’t change. We’ll use the fourth level Ability Score Increase to raise the giant’s Strength and Constitution each by one, which conveniently increases their bonuses each by one. Our berserker will have the 10 hit dice from the MM plus four more for the four added barbarian levels. This gives us a hit point average of 161 (14d12 + 70). What you might forget here if you’re not using Monster Maker is that because the proficiency bonus is +4, the giant’s Perception bonus is now +3 and its passive Perception is now 13. So far I have something that looks like this:
Keep in mind as well when you’re doing this that monster hit dice will always be based on size and its proficiency bonus will always be based on its challenge rating and not its levels or hit dice. Now, we can look at AC. The berserker gets the unarmored defense trait. The giant in the MM has a natural AC of 13, but with unarmored defense it has an AC of 14 (10 – 1 + 5), so we change the AC to 14. Let’s also add the Rage trait (3/day) and the Reckless trait. I use the Reckless trait from the NPC Berserker (MM p344) even though it leaves out the wording about Strength based attacks that Reckless Attack has. Our giant isn’t going to be making Dexterity attacks at a -1 penalty, and I find it simpler to look at during a battle. Lastly add the Frenzy trait from the Path of the Berserker, and the Multiattack, Greatclub and Rock actions from the MM. So far our stat block looks like this:
If the Monster Maker application doesn’t quite let you format something the way it would be in the Monster Manual, you can use HTML to format it. Note that in the stat block above I’ve used HTML to create the bullet points for the Rage trait. If you do this, do not use the enter key after each line, because it will space everything too far apart. It takes some getting used to if you’re a perfectionist like me and want the stat blocks to look authentic, but it comes pretty close for the most part.
Calculating the CR. Now comes the fun part. I’m going to assume you’ve read the rules for calculating CR in the DMG. I’ll go through the steps, but a basic knowledge of the method will help follow along. First I’m going to calculate the average damage per round. For that we need to know how much damage the hill giant berserker will do for rounds 1-3. I’m going to assume it is going to go into a rage on turn 1 with a frenzy. That means it gets +2 to its damage and on turns 2 and 3 it can use its bonus action to make a third attack. It can’t do this on turn one because it is using its bonus action to rage. With the +2 bonus and two attacks, the giant does 42 damage on turn one. Then on turns two and three it can do 63 damage. This averages out to 56 damage per round. Using the CR calculator I linked above I plug in the number in the appropriate place, along with the attack bonus of 10. Now before we figure in the resistances from the rage, lets see where our CR sits right now. Plug in 161 for the HP and 14 for the AC. I’m doing this because the next part is going to require we have some idea of the expected challenge rating. Right now without the resistances we’re at CR 8. We multiply the hit points by 1.5 since we have an expected challenge rating of 5-10 (10 being our guess earlier). So we change hit points in the calculator to 241 and calculate it again. CR 10! No further adjustments need to be done since all of the creatures traits and abilities are either accounted for or don’t impact CR. We’ve significantly increased the challenge rating of the original creature by adding some class levels.
Try adding class levels to a creature yourself, and let me know in the comments below what you come up with, and also comment if there is a topic you would like me to cover in a future post.