Help me downgrade a Marilith down to a 10 HD Lesser Marilith

[arkieNork]

Hi, I am looking to end up with something that's about on par with a Vrock.

I would like to keep the Large Size, tail constriction ability and 6 arms.

Not sure about what BAB, Ability Scores, Saves to give her, how to decide DC of her spells and which of her abilities should be cut.
Any advice would be welcome

[Telonius]

If you're just looking to reduce the HD, you'd be removing 6 Outsider hit dice (https://www.d20srd.org/srd/typesSubtypes.htm#outsiderType). That works out to a reduction of 6 BAB, and 3 to each of the base saves. Obviously you'd lose 6 HD worth of hit points.

DC of the spell-like abilities wouldn't change, unless you're changing the Charisma bonus. You determine the DCs by: 10+Spell level+Cha modifier.

Technically you would need to get rid of two of the given feats, since it no longer has the HD to support them. I'd probably go with Combat Expertise and Combat Reflexes.

Skills are going to be a real pain to figure out. I do not have time to do that right now, but I'd suggest figuring out how many skill points are in each skill mentioned in the monster entry, and working backwards from there. (If you even want to bother with it; you could just reduce everything by 6 if you want to save time and hassle).

After you've done that, you'd have your basic 10HD de-powered marilith. Whether it would be on the level of a Vrock? Probably not. I would take down a few of the higher-level spell-like abilities. Probably Blade Barrier would be the first I'd chuck. Change the Summon Demon to be the same as a Vrock's.

[Metastachydium]

I had the time. Here you go:

Hit Dice: 10d8+90 (135 hp)
Initiative: +4
Speed: 40 ft. (8 squares)
Armor Class: 28 or 29 (–1 size, +4 Dex, +15 or +16 natural), touch 13, flat-footed 24 o25
Base Attack/Grapple: +10/+23
Attack: Longsword +18 melee (2d6+9/19–20) or slam +18 melee (1d8+9) or tail slap +18 melee (4d6+9)
Full Attack: Primary longsword +18/+13/+8 melee (2d6+9/19–20) and 5 longswords +19 melee (2d6+4/19–20) and tail slap +16 melee (4d6+4); or 6 slams +18 melee (1d8+9) and tail slap +16 melee (4d6+4)
Space/Reach: 10 ft./10 ft.
Special Attacks: Constrict 4d6+13, improved grab, spell-like abilities, summon demon
Special Qualities: Damage reduction 10/good and cold iron, darkvision 60 ft., immunity to electricity and poison, resistance to acid 10, cold 10, and fire 10, spell resistance 19, telepathy 100 ft.
Saves: Fort +16, Ref +11, Will +11
Abilities: Str 29, Dex 19, Con 29, Int 18, Wis 18, Cha 24
Skills: Bluff +20, Concentration +22, Diplomacy +24, Disguise +7 (+9 acting), Hide +13, Intimidate +22, Listen +25, Move Silently +17, Search +17, Sense Motive +17, Spellcraft +17 (+19 scrolls), Spot +15, Survival +4 (+6 following tracks), Use Magic Device +20 (+22 scrolls)
Feats: Combat Reflexes, Multiattack, Multiweapon Fighting, Power Attack
Environment: A chaotic evil-aligned plane
Organization: Solitary or pair
Challenge Rating: 11 or 14
Treasure: Standard coins; double goods; standard items, plus 1d4 magic weapons
Alignment: Always chaotic evil
Advancement: 11–20 HD (Large); 21–48 HD (Huge)
Level Adjustment: —

Constrict (Ex): A marilith deals 4d6+13 points of damage with a successful grapple check. The constricted creature must succeed on a DC 24 Fortitude save or lose consciousness for as long as it remains in the coils and for 2d4 rounds thereafter. The save DC is Strength-based.

Improved Grab (Ex): To use this ability, a marilith must hit with its tail slap attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it succeeds on the grapple check, it can constrict.

Spell-Like Abilities: Caster level 10th. The save DCs are Charisma-based.

At will - align weapon, blade barrier (DC 23), magic weapon, project image (DC 23), see invisibility, telekinesis (DC 22), greater teleport (self plus 50 pounds of objects only), unholy aura (DC 25).

Summon Demon (Sp): Once per day a marilith can attempt to summon 4d10 dretches, 1d4 hezrou, or one nalfeshnee with a 50% chance of success, or one glabrezu or another marilith with a 20% chance of success. This ability is the equivalent of a 5th-level spell.

True Seeing (Su): Mariliths continuously use this ability, as the spell (caster level 10th).

Skills: Mariliths have a +8 racial bonus on Listen and Spot checks.

EDIT: I don't know how much the CR would go down, but this is what the numbers would look like by the book.

[Beni-Kujaku]

EDIT: I don't know how much the CR would go down, but this is what the numbers would look like by the book.

It's an Outsider, removing 6 RHD would normally reduce the CR by 3, for a total of 14. If you want to remove a bit more, an easy way to do that would be to add negative levels on top of that. "An affected opponent takes a –1 penalty on all skill checks and ability checks, attack rolls, and saving throws, and loses 5 hit points and one effective level or Hit Die" Adding one negative level, removing all SLAs that require a caster level above the current number of RHD (so at least Blade Barrier, Unholy Aura and Project Image), and reducing the natural armor by 1 should be enough to reduce the CR by one each time.

[Metastachydium]

Factoring a negative level into a statblock sounds messy. I modified stuff as per your suggestions above, marking features exclusive to the higher CR version in purple.

[arkieNork]

If you're just looking to reduce the HD...


I had the time. Here you go..


It's an Out...

Thank you all for the tips and the sample stat block. Very helpful and gives me a baseline to understand how to do this kind of stuff.

Is True Seeing an ability that is suitable for a CR9 demon or does that need to go too?

[Beni-Kujaku]

Thank you all for the tips and the sample stat block. Very helpful and gives me a baseline to understand how to do this kind of stuff.

Is True Seeing an ability that is suitable for a CR9 demon or does that need to go too?

True Seeing isn't a "powerful" ability in the sense that it's an immunity instead of a general defense like SR or DR, or an offense. At most, it will make the PCs lose an action. It probably won't have any impact if one of the PCs doesn't specialize in illusion, and even then, it makes the encounter a slight bit more puzzly but does not really impact the danger of the encounter. I think it's no problem. Also, Greater Teleport is a bit of a signature ability of demons, so it's more flavorful to keep it, even if you don't use it too much during the fight, it's always scary to see a freaking Marilith appearing in a split second before you.

[Saintheart]

Minor note, but losing HD "should" also lose the Marilith 2 points in an ability score, since it's dropping 6 HD and starts on 16 HD. Emphasis on "should", because I get that those are its racial ability scores and therefore baked in whatever the HD, but it might be worth considering. Of those I'd drop CHA by 2 since that impacts its spell-like abilities as they're CHA-based.

[arkieNork]

Minor note, but losing HD "should" also lose the Marilith 2 points in an ability score, since it's dropping 6 HD and starts on 16 HD. Emphasis on "should", because I get that those are its racial ability scores and therefore baked in whatever the HD, but it might be worth considering. Of those I'd drop CHA by 2 since that impacts its spell-like abilities as they're CHA-based.
Just so I am not misunderstanding, do you mean -2 to some ability score per HD or -2 for all -6HD?

[Saintheart]

Just so I am not misunderstanding, do you mean -2 to some ability score per HD or -2 for all -6HD?

Just -2 to one ability score for the total 6 HD drop. Monsters get stat increases just like player characters do, a +1 to one stat every 4 levels, but for monsters their total HD is their level. A Marilith starts at 16 HD, so dropping by 6 hd means it loses (or arguably should lose) the ability score increase it "would" have got at 16 HD and 12 HD (multiples of 4).

You can see similar mechanics at work with the feat selections: it dropped 6 HD, so it loses 2 feats off the standard monster.