In Tasha's Cauldron of Everything, the published Sidekick rules say (p. 142):

A sidekick can be any type of creature [...], but the challenge rating in its stat block must be 1/2 or lower. You take that stat block and add to it, as explained in the "Gaining a Sidekick Class" section.

The referenced section also says, among other things:

The starting level of a sidekick is the same as the average level of the group. [...]

Whenever the group's average level goes up, the sidekick gains a level. [...]

Whenever the sidekick gains a level, it gains one Hit Die, and its hit point maximum increases. To determine the amount of the increase, roll the Hit Die (the type of die appears in the sidekick's stat block) [...]

I assume "gaining a sidekick class" counts as "the sidekick gains a level" for the purpose of hit dice, and that isn't just talking about when the group levels up.
So does the creature start with the number of hit dice listed next to its hit points? Or does it have a pool of "free" hit points that don't come with hit dice?

For example, a kobold has "5 (2d6 − 2)" hit points listed in its stat block, and it doesn't mention "hit dice" as such. If a kobold becomes a sidekick to a 1st level party, does it start with a Hit Dice of 1d6 or 3d6?

It seems weird to have a sidekick starting out with 3 hit dice when it's only 1st level, but at the same time, a 1st-level sidekick kobold with 8 HP and only a 1d6 hit die also looks sort of odd.

• – V2Blast Nov 28 '20 at 20:26

## A sidekick starts with as many Hit Dice as noted in its stat block.

The rules about applying a sidekick class to an NPC do not state anything about removing Hit Dice from a creature before applying the class, nor does it specify the starting Hit Points as every player class shows. Rather, a sidekick starts with the Hit Die/Dice appearing in the stat block.

Quoting the relevant parts from Tasha's Cauldron of Everything (page 142), in the paragraph Creating a Sidekick:

A sidekick can be any type of creature with a stat block [...], but the challenge rating in its stat block must be 1/2 or lower. You take that stat block and add to it (emphasis mine), as explained in the "Gaining a Sidekick Class" section.

As an example, a 1st-level sidekick wolf would start with 2d8 Hit Dice. Similarly, a 1st-level black bear would start with 3d8 Hit Dice. In each case, those two sidekicks would gain an extra Hit Die (a d8) for each new sidekick class level.
The Monster Manual specifies that those dice are, in fact, Hit Dice at page 7, in the paragraph Hit Points:

A monster's hit points are presented both as a die expression and as an average number. [...] A monster's size determines the die used to calculate its hit points, as shown in the Hit Dice by Size table.
$$\\begin{array}{|l|c|} \hline \textbf{Monster Size} & \textbf{Hit Die} \\ \hline \text{Tiny} & \text{d4} \\ \text{Small} & \text{d6} \\ \text{Medium} & \text{d8} \\ \text{Large} & \text{d10} \\ \text{Huge} & \text{d12} \\ \text{Gargantuan} & \text{d20} \\ \hline \end{array} \$$
A monster's Constitution modifier also affects the number of hit points it has. Its Constitution modifier is multiplied by the number of Hit Dice it possesses, and the result is added to its hit points.

Sidekicks classes are not player classes. Each player class specifies the starting Hit Die and Hit Points at first level, but the sidekick classes do neither. You just take the stat block and "add to it".

# The starting hit dice equals the hit dice in the stat block plus the number of sidekick levels.

A hint is actually given to us in the sidekick stat blocks in Icespire Peak.

If we look at these classes, we notice that they all start off with 2 hit dice. That might seem weird, but lets consider building a sidekick from a commoner.

Commoners start with 1 hit die, and 10 in all their stats. If it's starting sidekick level is level 1 (average level of the party), then the question we must ask ourselves is as follows - is going from 0 to 1 sidekick levels "gaining" a sidekick level?

If you say no, then should you add the level 1 sidekick features to the stat block? Well, if you're a spellcasting sidekick, that would mean you don't get spellcasting. So that that logic doesn't follow. Going from not being a sidekick to being a sidekick must mean that you're gaining a sidekick level.

Based on the evidence we have above in the stat blocks provided to us, I think the logical conclusion is that we consider 0 to 1 to be "gaining" a sidekick level, which ends up with us having 2d8 hit dice, just like in our examples above.

An alternative argument to the same conclusion is to consider implications of this rule if you follow the accepted the answer above.

The starting level of a sidekick is the same as the average level of the group. [...]

If you accept the rule above, this would mean that that don't "gain" sidekick levels prior to your starting level.

If we take this logic further, and imagine a party gaining a commoner sidekick at level 12, this would add 0 hit dice to the commoner's stat block, since that would be defined as your "starting sidekick level." A level 12 sidekick commoner should not be weaker if acquired at level 12 than if acquired at level 1.

Lastly, this ruling is simpler and easier to apply - in my humble opinion.

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## Reasonably, the original hit dice would be replaced by class hit dice

I believe an appropriate reading of this section would imply that a 1st level Kobold Sidekick would have 1 hit die of 1d6. I base this on the generalization that Challenge Rating is not the same as Level, and to accept a monster's existing hit points as its starting hit points leads to absurd scenarios where a sidekick is the most powerful creature in a party.

## Detailed reasoning

Firstly, we can't inherently assume that every monster of CR 1/2, or any other CR, is a a uniform "base level" when we start applying sidekick features. As an example of this, a Monodrone Modron (MM p.224) is also a CR 1/8 creature, like a Kobold. However, the Monodrone only has 1 hit die of 1d8. Similarly, most CR 1/2 creatures have around 3 hit dice of various sizes, but Orcs (MM p.246) have only 2d8, a number of creatures have 4 or 5, and the Satyr (MM p.267) has the most with a full 7d8.

Secondly, the Dungeon Master's Guide advises that a single monster of a CR equal to the party's level poses a reasonable but not deadly challenge, and many other references throughout the DMG and the Monster Manual make similar references to that assumption. So we can't use CR as a 1:1 equivalence to "level" by assuming something like "CR 1/2 or lower creatures are level 1 as built," which would lead to the unusual scenario that a Kobold has a single "hit die" consisting of two dice. Instead, we should simply use a singular instance of whatever die is in the monster's hit point formula (a Kobold showing "2d6-2" hit points therefore has a 1d6 hit die).

Thirdly, Sorcerers and Wizards who would choose to put only an 8 in their Constitution would likewise enter 1st level with only one hit die of 1d6. The difference is that these character classes explicitly say you gain maximum hitpoints for the first hit die, meaning they would start with 5 hit points (1d6-1, maximized). That maximum hit point line is missing from the construction of a sidekick character, so its hit points should be the average (here, 3, or 1d6-1 taking the average roll of 4). I bring this up to point out that such a low number of hit points is far from unusual for 1st level characters that aren't explicitly built to survive a single hit.

Side Note: Tasha's does technically say you should roll for hit points on additional levels for side kicks, but taking the average is an accepted choice almost everywhere else when adding hit points, so I don't believe it's unreasonable to do the same for sidekicks. Similarly, if a sidekick is to be use as a player's primary character, taking the maximum for the first hit die is also a reasonable modification.

Lastly - as Tasha's Cauldron of Everything makes clear much earlier in the book in the Customizing Your Origin section - what is published carries with it "certain cultural assumptions." As a DM creating a Kobold Sidekick, you are now changing those "cultural assumptions" as well by allowing a monster such as a kobold, literally described as "easy prey for predators" and who "serve [evil dragons] as minions and toadies" (MM p.195), to receive a pseudo-adventurer's training and ability. The resulting change in hit points can be explained however you want it to be, in character or out, if you even need to, since it is hardly the most dramatic change the creature is undergoing:

• As character development: The more rigorous training it received in non-combat abilities means it is no longer as focused on life-or-death survival, and it's lost some of that drive to fight to the very last breath as a result.
• As character balance: Monsters normally don't get death saving throws, so a slight increase in their HP balances that out. Now that the monster is eligible for death saving throws, it should lose those additional hit points.
• As a counter to absurd situations: "You are not getting a Gnoll Sidekick who has 22 (5d8) hit points at first level."
• You seem to be answering a question I didn't ask, here. The book's text is pretty unambiguous that the creature's hit points are what's in the stat block as-written, plus a Hit Die+Con for each sidekick level it gains -- that is to say, a 1st level sidekick wolf will have 11+1d8+1 HP. The only question I'm asking is whether they have 3 hit dice to spend on HP recovery during rests, or just 1. I'll consider this as a frame challenge, but you're going to have to support the claim with some actual rules text rather than just arguing an appeal to consequences. – Darth Pseudonym Nov 30 '20 at 14:28
• @DarthPseudonym fair enough, I did branch off and answer a slightly extended question. I have posted a second answer that is less speculation and is derived from rules text directly. – MirrorImage Nov 30 '20 at 19:02

## A 1st level Sidekick, by definition, has 1 Hit Die

The Sidekick rules provide guidelines for substituting a creature stat block and its Challenge Rating with a more character sheet-like build and a Level. It offers the suggestion that a player could play this as their primary character but with much simpler mechanics than a traditional class or simply a second character under their control. The rules even refer to doing this as "Gaining a Sidekick Class", which makes it clearer that this creature should be bound to the same rules and expectations as a player character possessing a class.

Chapter 1 of the Player's Handbook includes a section titled Hit Points and Hit Dice which defines how those attributes are defined for a character. As relevant here (page 12):

At 1st level, your character has 1 Hit Die, and the die type is determined by your class. You start with hit points equal to the highest roll of that die, as indicated in your class description. (You also add your Constitution modifier, which you'll determine in step 3.) This is also your hit point maximum.

The Sidekick rules specify that "the starting level of a sidekick is the same as the average level of the group." Therefore, building up a sidekick from first level should revert it to having only a single hit die, gaining additional ones as appropriate when made to higher levels.