Designing Monsters

Use these guidelines to create an original monster to challenge your characters in combat. You can build a monster ahead of time or on the fly during a game session.

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Step 1: The Monster's Story

What does it look like? Is it intelligent? How does it react to strangers? In a movie, what would its attacks look like?

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Step 2: Determine Challenge Rating

To decide what CR will best challenge the adventurers, decide on the difficulty of the matchup and use the encounter-building guidelines in Designing Combat Encounters or use one of these shortcuts:

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Step 3: Customize Capabilities

Grant the monster any languages, senses, skills, saving throw proficiencies, movement forms, and traits that you think it should possess. You can use existing traits and other statistics for inspiration. 

Most traits don’t require a change to the monster’s game statistics. However, if your monster has healing, regeneration, or damage transference abilities, lower its hit points by between 20–30%.

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Step 4: Customize Combat Statistics

Consult the Statistics for Monsters by Challenge Rating table below and then modify the listed statistics as described.

CR	AC	HP	Proficiency Bonus	Ability Bonus	Attacks	Damage Per Round	Easy  DC	Hard DC	XP
0	12	3	+2	+0	1	1	10	10	10
1/8	12	9	+2	+1	1	3	11	11	25
1/4	12	15	+2	+1	1	5	11	11	50
1/2	13	24	+2	+2	1	8	12	12	100
1	13	30	+2	+2	1	10	12	12	200
2	13	45	+2	+3	2	15	13	13	450
3	14	60	+2	+3	2	20	13	13	700
4	14	75	+2	+4	2	25	13	14	1,100
5	14	90	+3	+4	2	30	14	15	1,800
6	15	105	+3	+4	2	35	14	15	2,300
7	15	125	+3	+4	2	40	14	15	2,900
8	15	135	+3	+4	2	45	14	15	3,900
9	16	150	+4	+4	2	50	15	16	5,000
10	16	165	+4	+5	2	55	15	17	5,900
11	16	180	+4	+5	3	60	15	17	7,200
12	17	195	+4	+5	3	65	15	17	8,400
13	17	210	+5	+5	3	70	15	18	10,000
14	17	225	+5	+6	3	75	15	19	11,500
15	18	240	+5	+6	3	80	15	19	13,000
16	18	255	+5	+6	3	85	15	19	15,000
17	18	270	+6	+6	4	90	16	20	18,000
18	19	285	+6	+7	4	95	16	21	20,000
19	19	300	+6	+7	4	100	16	21	22,000
20	19	315	+6	+7	4	105	16	21	25,000
21	20	330	+7	+7	4	110	17	22	33,000
22	20	350	+7	+8	4	116	17	23	41,000
23	20	375	+7	+8	4	125	17	23	50,000
24	21	400	+7	+8	4	133	17	23	62,000
25	21	425	+8	+8	4	141	18	24	75,000
26	21	450	+8	+9	4	150	18	25	90,000
27	22	475	+8	+9	4	158	18	25	105,000
28	22	500	+8	+9	4	166	18	25	120,000
29	22	550	+9	+9	4	183	19	26	135,000
30	23	600	+9	+10	4	200	19	27	155,000

 

Armor Class

You can raise or lower the monster’s Armor Class by one or two points without altering it in any other way. If you change its AC by 3 or more points, you should reduce or raise its hit points or damage per round by 5% per point of AC you varied from the base AC.

Hit Points

You can raise or lower the monster’s hit points by 10% without altering it in any other way. Beyond that, you should reduce or raise its AC by 1, or its damage per round by 5%, for every 5% of hit points you varied from the base hit points.

Ability Bonus and Attack Bonus

The Ability Bonus column represents the monster’s highest ability modifier, usually the one it uses for its main attacks. You can raise or lower this bonus by 1 or 2 from the suggested value in the table. 

A monster’s Attack Bonus is usually its best Ability Bonus plus its proficiency bonus.

Attacks

Most low-level monsters (CR 1 and lower) make one attack on their turns, while higher-level monsters make more attacks per turn (either as part of a Multiattack or with a combination of bonus actions and reactions). Monsters that occur in greater numbers should have few attacks, while lone monsters can have more of greater complexity.

Damage Per Round

The Damage Per Round column represents how much average damage a monster would deal per round if all of its attacks hit and its foes failed their saving throws against it on all of its actions. Divide this total among all the monster’s actions, bonus actions, reactions, legendary actions, and damaging traits. 

This number can be raised or lowered by 3 or 4 points without changing the monster’s CR. For a monster in your home game, it’s not always necessary to convert a damage total into a dice expression, but you could.

Conditional Damage

Some attacks deal extra damage in some circumstances: for instance, a creature may deal extra damage to a grappled target, and a successful sting attack may deal additional poison damage only if the target fails a saving throw. As a rough estimate, assume that such attacks deal their extra damage half the time. Thus, each two points of conditional damage only counts for one point of damage against the Damage Per Round budget.

Some attacks deal ongoing damage that might last for any number of turns. Assume that ongoing damage occurs once and then ends.

Special Attacks

You can vary a monster’s attacks by giving them tricks like area effects, limited-use abilities, and attacks that inflict conditions.

Area Attacks

A hellhound’s breath, a cleric’s blade barrier, and a balor’s aura are area effects that can affect multiple opponents. If a monster can use an area attack every turn, reduce the damage it deals by about 70% compared to a normal attack. 

Limited-Use Abilities

Abilities that can be used once per day or once per short rest, or have a recharge of 6 or 5–6, are limited-use abilities. They typically allow a monster to exceed its damage-per-round budget on one turn, making up for it by dealing less damage on other turns.

For every two points of damage that a limited-use ability exceeds the damage per turn budget, reduce the total damage dealt on other turns by one.

Inflicting Conditions

Many monsters have other tricks besides damage: they blind, grapple, knock their opponents prone, or deal other such dirty tricks. 

Minor conditions primarily affect movement or ability checks. Grappled, prone, and rattled are minor conditions. Treat a push or pull like a minor condition. When budgeting damage, you don’t need to take minor conditions into account.

Moderate conditions often impose disadvantage on the target. Blinded, frightened, poisoned, restrained, and slowed are moderate conditions. Treat a moderate condition as the equivalent of damage equal to the monster’s Challenge Rating, or double if it can affect multiple characters.

Severe conditions prevent a creature from taking the actions it wants to take. Charmed, confused, incapacitated, paralyzed, petrified, stunned, and unconscious are severe conditions. Treat a major condition as the equivalent of damage equal to double the monster’s Challenge Rating, or triple if it can affect multiple characters.

Difficulty Class

To calculate the DC for a specific monster’s ability, add 8 + the monster’s proficiency bonus + any one of the monster’s ability bonuses. 

The Statistics for Monsters by Challenge Rating table contains columns for Easy DC and Hard DC. Use the numbers in these two columns to judge whether the DC of your monster’s ability is too high or too low to properly challenge opponents, and whether you should consider modifying the monster’s ability score. If you’re creating a monster on the fly without figuring out all the details, just use the DCs in the table without bothering with the calculations.

The Easy DC column represents a saving throw DC that gives most characters a chance to succeed. Use this DC, or a DC within 1 or 2 points, for effects that inflict severe conditions or that inflict moderate conditions for more than a turn.

The Hard DC column represents a DC that many adventurers are likely to fail. Use this DC, or a DC within 1 or 2 points, if the effect deals damage, a minor condition, or a short-term moderate condition.