How to increase a monster's CR without adjusting its flavour too much?

Background

I have a player who has a level 8 Half Orc Paladin (STR 16, CON 18, CHA 14, Vengeance oath, Sentinel and Orcish Fury feats, no magic items) whose backstory involves running away from his home town when he was young (12 or so?) when his orcish father turned up with a horde of orcs looking for him. He hasn't seen them since and he's now in his 30s or so.

I was going to have his "father" turn up with a horde of orcs (15 or so) and demand his "son" back, mirroring his backstory. I was planning on guiding the narrative to the paladin PC having an honour duel with the Orc War Chief (MM, pg 246). I have a player and group who are into narrative over gaining XP (in fact we're using milestone XP) so I think this will go down well (though if they just decide to fling fireballs at the orcs, then that's what happens; I'm not going to railroad this too hard).

Given that this will be a BIG backstory moment for the player, I want to make sure this duel is suitably epic. I want it to be winnable, but also deadly. It should be a skin-of-his-teeth victory. I imagine (since Chaotic Evil orcs don't have honour) that when the War Chief starts to lose, the other orcs might join in, or if the War Chief ends up on < 10HP, he might even try to run away, but we'll see how that goes. I imagine the rest of the party will join in if this ends up happening, but until then, I imagine the duel will be a one-on-one fight between the paladin and the War Chief.

Problem

Anyway, if I want this fight to be deadly, a CR 4 monster probably isn't going to cut it compared to a level 8 paladin (this is based on the encounter design table in the DMG, pg. 82). But at the same time, I like the War Chief's abilities and flavour and such, so I'd rather not pick a different creature.

Ideally, this monster should be about CR 6, but I wonder if just bumping up his health, AC and attack bonus will be enough, or whether this wouldn't really make him that much more threatening over the course of the duel (this is me trying to follow the table in the DMG, pg. 274). Even though this PC has none, magic items exist in my world so the War Chief could have one of those, but would a +1 weapon or whatever really change things that much?

Question

How can I change the stats of the Orc War Chief to increase the CR from 4 to 6, without changing it drastically like adding spellcasting or lair actions or otherwise messing with the monster's flavour?

Just fake it

You're asking for an epic one-on-one duel for a player, and it has to feel suitably epic. Sadly enough, CR ratings are only a rough estimate and one-on-one duels in D&D are extremely 'swingy'.

Two misses on the players end or a crit on the monster's will likely make the encounter completely impossible. On the flip side, if the player crits once, they may very well cut the encounter time in half. If they don't crit, it'll likely result in an extremely long drawn out fight of "I hit, you hit, I hit, you hit." It's not going to be suitably epic, it's just going to be boring for everybody involved.

Instead, for such a one-on-one encounter, it's far easier if you just fake it. Write down the half-orcs HP and AC beforehand, and scribble down some fake to-hit and damage rolls, depending on how long you want the fight to be. Throw in a crit in there, to make things "really scary", and add some misses as well. At the end of list of fake rolls, the player should end up with 1 or 2 hp, for that "just made it!" feeling. Focus on describing the action narratively and just throw fake dice-rolls behind your screen and read off your list, the players don't need to know.

After the player is near death, just have the Orc either go down, or flee after the next hit, and make him miss if the player ends up missing. Alternatively, have the Orc try to persuade the character to join him, so they can rule as father and son. (Noooooo!)

In conclusion, is it possible to make a CR monster that will provide an epic encounter for a single player? Possibly, maybe. Is it going to work? Nope, because the dice are going to go "welp, this encounter is now over" and everybody is going to feel dissatisfied with the fight.

I've done this before with an epic devil fight, my players still talk about that fight and how the paladin managed to banish it with his last breath before collapsing exhausted, and they never needed to know that I was 'cheating' it.

• While a like this approach and have used it myself it does take a certain kind of DM, running a certain kind of campaign to pull it off. If you never use a screen or fudge dices rolls I wouldn't suggest starting it for this fight or your players might feel cheated. Oct 22, 2018 at 9:38
• I hadn't thought of this, I like this frame challenge. Incidentally, ending up with 1 HP will be really easy given that the PC is a half-orc with Relentless Endurance, so I could even just roll real damage and when he has to use Relentless Endurance to stay at 1 HP, that's when I can have the orc go down or flee or whatever... (I guess I'd describe the orc getting wearier parallel with the PC's health % so that it seems plausible that he'd go down on the next hit) Oct 22, 2018 at 9:47
• "just throw fake dice behind your screen" - Wouldn't you throw real dice, and then just ignore the numbers that come up in favor of the precomputed ones? Oct 22, 2018 at 23:25
• That's what I meant by throwing fake dice, Aroth. I'll make it more obvious. Oct 23, 2018 at 6:34

The encounter tables are designed for parties of three to five characters. A CR4 monster is a challenge for 4 fourth level characters. The DMG says to adjust for smaller parties.

The preceding guidelines assume that you have a party consisting of three to five adventurers. If the party contains fewer than three characters, apply the next highest multiplier on the Encounter multipliers table. (DMG p.83)

The XP for an Orc War Chief is 1,100 %times; 1.5 = 1,650. This is well above the Hard threshold for a level 8 character. Note: The War Chief also has 11 hit dice. For a solo battle, this might push it into the deadly range.

• That's a good point; at the very least, aiming for CR 5 rather than 6 might be more appropriate (the XP earned is irrelevant since I'm using milestone levelling, so I don't need to worry about that side of things, at least). I think I'll still bump the stats up slightly (HP at least) just because I know what paladins are like with their nova damage... Oct 22, 2018 at 9:57
• @NathanS - The XP calc is solely for determining encounter difficulty in accordance with p. 82 of the DMG. Rolling his HP instead of taking the average may bump his HP accordingly. Oct 22, 2018 at 10:00
• That's another good point; giving him above-average HP with the hit dice he already has might do the trick without needing to actually add anything else. Oct 22, 2018 at 10:10
• @NathanS Wait, the answer says "this encounter by the XP guidelines is already above 'hard'", and your response is "ok, so I'll bump it less". Maybe you should instead run some simulated combats? :p
– Yakk
Oct 22, 2018 at 17:24

Unfortunately 5e does not have set rules on this unlike previous editions. However my favourite way to beef up a monster manual enemy is to add class levels.

3 levels of Fighter (Champion) would grant Great Weapon Fighting Style, Second Wind, Action Surge and Improved critical. Barbarian would also suit but flavour to your preference.

Give magic items

As you suggested some higher level magic items would definitely help. A +1 weapon would close the gap on what I see as the war chiefs biggest weakness against a Paladin. Low attack bonus will struggle to hit the paladin regularly. Assuming he has an AC of 20 or above as most lvl 8 paladins would.

Improve Base Stats

You could choose to increase the War Chiefs base stats. A strength of 20 or even higher would make him feel like an epic enemy.

Give Feats

Add a feat or two to increase his combat ability without modifying the base class. Great Weapon Master would be a great choice.

Proficiency Bonus

As you are increasing the CR of the creature its proficiency bonus will also increase. For a creature between CR5 and CR9 this will be a +3.

Alternatively

Don't use the War Chief and just make a npc based on half-orc racial abilities (Player's Handbook) reskined as a full orc or the Orc racial traits from Volo's Guide to Monsters. This is my normal approach for BBEG or significant enemies. I find class levels allow you to multiclass to get exactly the feel for the class you want. Barbarian 2/Fighter 6 would feel like an angry orc war chief to me.

Monster Advancement Rules: these are from Pathfinder, since there are no official rules for 5e, but I find they translate fairly well with a little work.

• I like the suggestion of creating an NPC using PC stats, or adding class levels to the monster. At the very least, even if I only add Rage, that will suit the flavour and will help defend against at least some of the paladin's nova damage... Oct 22, 2018 at 9:59
• Can you expand on your recommendation to alter the monster's proficiency bonus? The MM has clear criteria relating proficiency bonus to CR, so I'm curious why you're recommending to deviate from that. Oct 22, 2018 at 12:38
• @Pyrotechnical TBH, I forgot there was proper rules for that. I've modified it to take them into account. Oct 22, 2018 at 12:42

I'm normally against this, but if you want an epic battle here, you really need to simulate the fight. That will tell you how much you need to boost the CR (if any) in order to make the fight a challenge. Paladins in particular have a huge alpha strike potential in a multiple-smite attack round.

We can do it with math without playing it out. How far the average fight is from an even fight tells us something, if not everything we want to know.

Assuming the Paladin has a 1d12 axe and heavy use of smites, and the Paladin uses his Vengeance features:

• STR 16 (+3 hit/damage), prof (+3).
• 3 2nd level slots (used to smite, 3d8×3, cannot miss, can crit) and 4 1st level slots (2d8×4).
• Fury (+1d12, cannot miss).
• 1d12+3 damage on a hit, 2 swings per round

• +6 to hit.

• I'll assume Plate armor (AC 18) on the Paladin.

The Paladin's HP should be about 8×4 + 6×8+4 = approx 84, plus 40 points of lay on hands (burning an action to gain +50% of your max HP is presumed to be efficient).

On the other hand, the Warchief. 93 HP, +6 to hit, 1d12+1d8+4 (aka ~15) × 2 damage (so 30 if everything hits).

Warchief accuracy is 12+/20 or 0.45, so 13.5 damage per round.

Paladin accuracy is 10+/20 with advantage or 80%, so 7.6 damage per round, plus up to 83 burst damage from Fury and Smites (and another .8×9.5 from Relentless Endurance).

(84+40)/13.5 is 9.2 rounds for Warchief to kill Paladin.

The Warchief crits 0.1 times per round for +11 damage per crit, or +1.1 damage/round (but high swing). That drops the Paladin down to having an average of 8.5 rounds to win.

The Paladin crits ~0.1 times per attack for +6.5 damage, but can also burn L2 Smites for +13.5 and Fury for +6.5.

The Paladin making 2 attack/round does 15.2 DPR. But every hit triggers smites and fury. First hit is +20 damage. Next two are +13.5. Each one after that is +9 damage.

The Paladin has to lay on hands at least once and abjure enemy, and has 8 rounds (on average) to win. Over 6 rounds the Paladin gets 9.6 hits; enough for special abilities. So 13.5×3 + 6.5 + 9×4=81 bonus damage.

$$15.2\times6 + 81 = 172.2 \text{ damage}$$

The Warchief has 93 HP. So the Warchief drops around round 3-5 with the Paladin at 1/3 HP (or more if they layed on hands)

We can uptune the Warchief. First, give the Warchief a +1 axe, stolen from his mother's family. DPR goes up to 16 just from that.

The Warchief can start with a spear throw, which can tilt the battle if they start more than standard movement speed apart.

The big problem with my model above is Hold Person. +2 Wis saving throw to defend against a a save-or-lose spell (2 failures for first coup, then 1 failure per coup, and best case is they lose a turn). I guess at 12 DC this isn't too bad (55% chance no effect, 25% orc loses a turn, 20% chance Paladin gets at least 1 coup).

We could balance this by having the Orcs swarm in if you cheat with magic that way. The duel can even have that as a rule; no "using magic to make warchief weak". "Go ahead and magic yourself strong, I stronger".

So we can work backwards.

1. I'd work out how long you want the fight to be. You know the Paladin's HP (including Lay on Hands) is 124. Suppose you want the Warchief to go down on the Paladin's 5th turn. That means if the Warchief gets 5 attacks, the Paladin should still be standing. So 124/6 is about 20 DPR, 124/7 is 17. So 17-20 DPR should threaten the Paladin seriously over a 5 round fight.

2. Work out the Paladins naive DPR. Over 5 rounds, the Paladin gets 8 chances to drop a smite or the like. We'll assume they get at least 4, for 13.5×3+9+6.5 or 56 smite and fury damage. They also swing their axe 8 times for 9.5 damage/hit. At +6 to hit against AC 16, so 80% accuracy, so 6.4 hits times 9.5 is 60.8. 0.8 crits means they are uncertain, and they do at least 2d12+2d8 (22) damage, for another 17.6 So the Warchief needs 134.4 HP to be dropped on average on turn 5, assuming paladin just chain-smites and never crits.

Smart paladins can do better than this (bonus action smite spell, for example, or doing big smites on crits, or go for a hunter's mark for 1d6 per swing and lucky concentration, or bless for even more accuracy).

A +1 Greataxe means 2x +7 to hit (11+) at 1d12+1d8+5 damage (16) for 17.1 DPR. That is in the window required to drop the Paladin after 7ish rounds.

Just up the Warchiefs HP to 130 and call it a day. It should be a nail-biter; if the PC gets unlucky, the Warchief can win. If the PC plays smart, the Warchief should lose by a non-zero margin. If the PC doesn't go all-in, the PC is likely to lose.

A character who had to use most of their spell slots on smite and lay on hands won't think it is an easy battle.

Have the war chief play dirty.

I like what the existing answers have stated, but I wanted to add the solution of making the war chief play dirty. Nothing says 'epic fight' like whenever the hero is actually disadvantaged from the start and is still able to triumph. A little poison somehow slipped to them right before the match starts, or perhaps some sort of hindrance meant to slow them down in a not-so-visible way.

It could be this moment when the war band finds out their leader has been swinging around an "Orcbane Axe" that deals additional damage to anyone with orc blood, and so he's been maintaining his status of 'strongest orc' through treachery!

Now I have finally run this encounter, I thought I'd provide an answer explaining how I did it and how it went.

Keeping track of damage dealt

Inspired by Theik's answer, I decided to fake some of it. Since ravery and Yakk both pointed out that I didn't need to boost the CR like I thought, I decided not to change the stats too much, although I did take a suggestion from linksassin's answer and I gave the War Chief just the Rage feature so that he might last a bit longer.

How I did it was to keep track of the damage that the paladin PC dealt, rather than keeping track of the remaining HP like I usually do. I raged half way through the duel, and tried to describe the War Chief's condition (how bloodied or weary he looked, etc) proportionate to the PC's remaining HP (although the PC gave themselves a chunk of HP back via Lay on Hands at one point, but it didn't seem to affect the narrative of the War Chief's condition too much).

A couple of crit-smites (in the same turn, no less) brought the damage dealt well above the 93 HP of the MM War Chief with average HP, but not quite over the maximum HP of 132 (derived from assuming maximum value of the War Chief's hit dice). The War Chief crit on the next turn and would have brought the PC down to 0 HP but for Relentless Endurance. These were the two things I was waiting for.

The fact that the damage the PC dealt was between 93 and 132 means it was now plausible for the War Chief to die, and that the PC survived only because of Relentless Endurance made it feel epic (because he would have been dead otherwise, also he just survived a crit). The next attack I decided would kill the War Chief. It so happened that the next attack was from the Orcish Fury feat, but unless he missed 3 times in a row, that War Chief was gonna die (and if he did miss 3 times in a row, I'd have had the War Chief flee because he was sure that was gonna kill him).

With the War Chief dead, the other orcs charged. The party took out most of them, but a few javelins took out the paladin PC (the last one I rolled hit him, the others all missed, so that felt epic as well) before the party mopped up the rest of the orcs and saved the paladin before he bled out (well, actually he succeeded two death saves already with no failures, but it still felt epic).

Although various other answers provided me with useful feedback and suggestions, I eventually realised that what I was really going for was a feeling. The feeling of an epic duel. Theik was the first to point that out and suggest how to more reliably guarantee that feeling, which I eventually used a variation of that I described above (since I roll openly, following Theik's advice exactly wasn't quite possible).

There are criticisms of my approach, such as how it can still be swingy (such as if the War Chief forced the PC to use Relentless Endurance on the first attack of the War Chief's multiattack, then hit him again, then the War Chief wins). But it worked for me so hence I detailed it above, and if anyone wants to have more control in "faking it", see Theik's answer.

Scaling

I'd suggest not thinking about what to add but how to scale. Especially useful is page 274 of the DMG (Monster statistics by challenge rating). Since you don't want to add special abilities or change the flavour, you'll probably want to adjust the basic stats: AC, HP, Attack Bonus, Damage.

The Chief is a pretty straightforward monster: even by using the direct stats the CR is calculated at level 4 so it can be assumed the special abilities do not affect the rating too much, especially in the context of a solo battle. We see that the AC is a bit high, especially considering that it has 3 good saving throws (which is equivalent to +2 AC). HP is a bit low, damage is average, attack bonus a bit high.

We'd like to keep this as we scale up; so if we pop everything two steps up we need to reach AC18 (with the saves, so base 16), HP ~120, attack +6, damage ~40; and indeed, a quick calculation shows a CR of 6. Now the AC staying the same feels a bit wrong, so maybe bump it to 17 and possibly increase the WIS save a bit. To counteract that (although not strictly necessary) we could lower the hp a bit.

Another tweak would be giving the monster legendary resistance (and lowering the actual hp to compensate). This can be used to fine-tune the fight in real time. Did the boss fail a hold person in the first round? Have it succeed instead (or after 1 round). More importantly you don't have to use it so if they fail a save in an appropriately climatic moment you can let it as it is.

It's not crucial to figure out exactly how they got these stats although it can give some flavour, especially if the players get to loot the body. Maybe the increase to-hit is a +1 weapon but maybe it's an extended Bless from the shaman; but first figure out the numbers and then the cause.

Environment

Compare: an archer in a tall tree that takes 1 round to climb (athletics DC 15, or 2d6 falling damage) vs an archer in 10ft. Obviously the CR is not the same; tweak the environment so that it benefits the chief. Perhaps he's a decent archer so after taking damage he smashes the bridge they are fighting on and starts shooting - paladins cannot divine smite in range. Or he has a potion of fire immunity/resistance and sets the field on fire. This could be tricky to balance; which brings us to:

Playtest

Especially since it's an 1-to-1 fight that's meant to be epic you need to simulate it. CR/encounter calculations are assuming a party of 4, which will be much more diverse than a party of 1. Luckily a paladin has a mix of abilities - but it's still a good idea to see how the fight plays; build your own lvl8 paladin and fight!

On that note, as ravery mentioned, a CR6 monster for a single lvl8 character is 50% deadlier than a deadly encounter. Note that a CR X monster is (on average) a medium encounter for a party of 4 characters! So in this case I'd aim for something between CR4 and CR5.

One fight, two fights, three fights

Haven't thought the following through - it might be worth considering the fight in stages, especially if you want more control over the execution; what does it mean to have an epic duel? Maybe the chief starts toying with the paladin, and he gets an advantage; then the chief gets serious and starts hitting hard, perhaps chasing the paladin around. But this is exhausting and finally the paladin gets the upper hand, and defeats the chief.

But this doesn't have to be one monster. Maybe the first one is a CR3 monster with not that great attack; then you switch (without telling the player) to a CR4 with high attack, not so much hp, and finally, either when the player deals enough damage or X rounds pass, to a regular CR4 chief (and then the other orcs join the chief, who is fully refreshed - a shaman heals him?). In a sense, it's like building a dungeon; you don't rely on a single monster to be both the initial guard, a puzzle, and the final boss but you build each step separately.