I am new to playing 5e, and my DM is also new to DMing 5e (although they have extensive prior experience as a 3.5e DM). We are interested in using the Sidekick rules presented in Tasha's Cauldron of Everything to round out a party since I am the only player. My character is a Fiend Patron Warlock whose Patron is an archdevil. The most thematic starting Sidekick I can think of is a low-level devil sent by my Patron both as a boon and also to tempt me into more evil deeds in order to hasten my corruption. This keeps the spotlight on my warlock and hooks into my existing backstory quite nicely.

I searched dndbeyond and only found 2 devils with CR between 0 and 1/2: The Lemure and the Nupperibo. Both seem incredibly stupid and uncharismatic, and thus unlikely to be much of a corrupting influence at all (instead it just seems like a body in a fight, and a liability in any civilized setting).

Expanding the search to CR 1 helped me to find the Imp, which is just barely illegal, but thematically perfect. 14 CHA and 11 INT make it easy to RP as a slow, steady corrupting influence, while Shapechanger helps it from becoming a huge liability when I need to spend time in civilized areas.

I think the best option is to tweak the imp until it is CR 1/2, and then give it sidekick levels from there, but I'm open to frame challenges (especially from anyone who played with UA sidekicks which did allow CR 1, who might know the Imp is fine as is, or that the Imp is especially problematic in ways which will still be present even at CR 1/2).

I plugged the stats into two different CR calculators for the base Imp, then played with options until I got CR 1/2. I was surprised to find that both calculators agree that reducing the AC by 1 is all that is required to bring it down to CR 1/2 (Offensive CR of 1, Defensive CR of 1/8). I tried to follow along with the DMG and it also looks right to me:

Defensive CR:

  • Actual Hitpoints of 11, Effective of 22 due to resistances/immunities means it is in the CR 1/8 range)
  • reducing actual AC from 13 to 12 means that Effective AC drops from 15 to 14 when factoring Magic Resistance, which means no adjustment from AC since CR<=1 is expected to have 13+-1 AC.
  • The base Imp barely falls outside this range, which increases Defensive CR above 1, which is what pulls the entire creature up to CR 1

Offensive CR:

  • Damage/Round is 15, which is barely base Offensive CR 2
  • Damage is primarily based on Save DC of 11, so Offensive CR gets adjusted downwards by 1

Given that this Sidekick is going to be with me for the duration of the campaign (and thus matters a lot more than any monster in a one-time combat encounter), and that the UA Sidekick rule was deliberately scaled back from 1 to 1/2, I want to be sure I didn't go astray for my first attempt at adjusting Monster CR.


3 Answers 3


Monster Challenge Rating is not exact science

The very fact that you can change AC by one to change the CR (on paper) shows the limits of the approach. If the AC-1 imp is okay the normal probably is, too. I know that you have to set a limit somewhere, but really there's a continuum and the AC change of one is not a far way on the continuum. Either they're both okay in play, or not, or they're both approximately at the limit.

As a single player you're probably fine

I used some "legal" sidekicks (humanoids with CR 1/4 to 1/2) and they mostly weren't that impressive. If you consider the sidekick as an additional person in the party, it seems you won't be easily unbalancing the encounters. Since you're alone you're already at a disadvantage compared to a diverse party, so it's even less critical.

The imp is offensively skewed.

The imp's offensive CR is a lot better than the defensive. This is a typical problem in monster design which I try to avoid. Now, since the imp is already better on offense, reducing AC is not the solution since that makes the difference worse. I don't know about later levels, but at the beginning levels a sidekick with offensive CR 2 will overshadow player characters since it can easily wreak havoc on appropriate opponents. So, if you want to reduce the CR of the imp, you should probably reduce the damage to the appropriate level to get there, taking 1d6 or 2d6 off the poison damage will do it. Then again, you're the only player, so the overshadowing problem is not really critical if you don't mind your imp doing more damage than you.

  • \$\begingroup\$ Can you explain why you think the Imp is offensively skewed? It seems to match the Defensive CR in that it is on the extreme low end of CR 1. If it had 1 less DPR, it would be base CR 1, modified down by 1 (to 0?) because of the low save DC (not to mention you can only make the save if the attack hits). I get that damage is big but (as someone with no 5e play experience to judge this accurately) it seems like it shouldn't land that full damage very often at all. \$\endgroup\$ Commented Jan 1, 2021 at 15:26
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    \$\begingroup\$ @stevenjackson121With offensive 1 and defensive 1/8 it is multiple steps ahead offensively (3 steps). One step below 1 is 1/2, not 0. Whether or not the full damage is dealt often is unimportant. That is already considered by accounting for attack bonus and save DC. \$\endgroup\$
    – Anagkai
    Commented Jan 1, 2021 at 15:56
  • \$\begingroup\$ The calculators I used actually disagreed on what happens when you adjust CR due to DC or AC for fractional CRs. One increases or reduces it by one step (1/8 -> 1/4 or 1 -> 1/2) and the other increases or reduces it by 1 CR (1/8 -> 1 1/8 rounds to 1, or 1 -> 0). Looking at the DMG, RAW seems to be increasing or decreasing by 1, not one step (which does skew things a lot). Do you recommend treating it as a 1 step adjustment instead? That would make it a lot easier to tune without touching AC, since I'm treating the 1 point of AC as bringing up Defensive CR all the way from 1/8 to 1 \$\endgroup\$ Commented Jan 1, 2021 at 16:07
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    \$\begingroup\$ @stevenjackson121 I don't have my DMG at hand but I was always very sure that one step was e.g. 1 -> 1/2. Anything else doesn't make sense. CR 0 offensively means almost no effective attacks and CR 1 means a good fight for 4 characters of level 1. Changing the Attack bonus from +3 to +1 does not suddenly make the CR 1 monster almost harmless. \$\endgroup\$
    – Anagkai
    Commented Jan 1, 2021 at 16:16
  • \$\begingroup\$ That clarifies that I really should be adjusting the Offensive CR. I was treating the base Imp as Defensive CR 1, but if the Defensive CR is really more like 1/4, then reducing damage seems like it is certainly the way to go. I like the suggestion to reduce by 1d6, thanks for walking me through everything! \$\endgroup\$ Commented Jan 1, 2021 at 16:43

You've indicated that you're open to frame challenges, so I'd like to point out that the most common way for a warlock to get an imp is to take the Pact of the Chain. If you do this, it will free up your sidekick slot for something else. Your real sidekick can then follow the normal rules and you won't need to issue a bunch of houserules for how to level it.

If that's not an option for some reason, my second suggestion is that you choose one of the existing sidekick classes and retheme it as some sort of shadowy devil-person, keeping all the same stats. That also will save you from having to issue house rules about balance.

If that's also not an option, my third suggestion is that you keep the imp, accepting that its CR is slightly above the recommended range. In a one-player game, you don't really have to worry about balance as much, because there aren't any other players who might feel bad if you play something that's overpowered.

  • \$\begingroup\$ The sidekick classes are supposed to be applied on top of CR 1/2 or lower monsters, so I won't need house rules during levelling. I will be using one of the existing sidekick classes as is for all future levelling, the only tweak I want to have to make is to the initial imp statblock so that it doesn't start too strong. I did consider Pact of the Chain, but I'm more interested in an Imp sidekick that can level alongside me. \$\endgroup\$ Commented Jan 1, 2021 at 16:53

As an alternative to attempting to adjust the stats of an existing devils, you can instead re-flavor another creature.

This is a common tactic for DMs that run homebrew games. They find a creature in the Monster Manual that has appropriate stats, and change the name of the creature, and adjust the superficial attributes as necessary, such as alignment and languages known, and renaming special abilities to be more thematic.

In the case of wanting an Devil of some kind where the Imp has too high of a CR, you could simply take a creature such as a Sprite (CR1/2) or an Owl(CR0), and just change the name. Since it will be using the Sidekick rules, its base strengths and weaknesses aren't as important for combat.

  • 2
    \$\begingroup\$ Thanks for the suggestion! That's certainly a valid alternative to tweaking an existing monster that is much better than inventing a monster from scratch. The Sprite is a bit confusing to me because of how different her damage is from what I'd expect based on ability scores. I don't know how to scale a fixed 1 damage when leveling up (if it scaled with Dex, wouldn't it already be much higher?), and I'm also a bit wary of having flight + ranged attack (with any damage value) at the start. I do also like both Blindsight and Shapechange, so in this case I do think starting with the Imp is easiest \$\endgroup\$ Commented Jan 1, 2021 at 17:46
  • \$\begingroup\$ The Sprite is just an example, any CR1/2 or lower creature will work, although some may not work as well. The base Sprite deals 1 point of damage mostly for balance purposes, and a flat 5 points of damage, with a +6 to hit, plus a rider effect that forces a save is a bit strong for a CR 1/2 creature. Once it starts advancing though, it's probably going to be OK to allow its Dex bonus to its damage. \$\endgroup\$ Commented Jan 1, 2021 at 18:01

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