Please Help: Stats for Construct Monster

[sabelo2000]

Playground,

Please Halp! My group met for Session Zero this evening, and my players have decided they'd rather play 5e than Pathfinder. I've got no problem with this, it just means I have to convert my adventure materials to 5e stats, except this monstrosity:

https://photos.google.com/album/AF1QipMbDOsq9R6lYTx-9yP0uYtao6p5no3z99JDeBhd/photo/AF1QipPfIJH_pq5TkuY6YjUSJ3OGO3SeKcfyfuNqUSyW

https://photos.google.com/album/AF1QipMbDOsq9R6lYTx-9yP0uYtao6p5no3z99JDeBhd/photo/AF1QipM3wfoxVvc89jd0ce1OtubPTpqjeU7YW5cDlr3j

[Description: a horseless carriage, which has come alive as a horrible mantis/spider/anglerfish ready to devour things]

I'm looking at a Huge animated object, my target is CR 9. I am lost creating monsters for 5e, and our first game is in a week! Please help!

[sabelo2000]

Details I'd like to keep for this monster:

* CR 9-ish
* Construct Traits
* Free-Willed
* Multiattack (Claw/Claw/Bite)
* Poison (Bite)
* Improved Grab (Bite)
* Swallow Whole
* Speed 40-ish
* Huge size, appropriate damage on natural attacks

[Wizard_Lizard]

i mean you could always homebrew one if you have time.

[sabelo2000]

i mean you could always homebrew one if you have time.

My difficulty there is I have no experience homebrewing and balancing monsters for 5e, just Pathfinder.

[Vogie]

Details I'd like to keep for this monster:

* CR 9-ish
* Construct Traits
* Free-Willed
* Multiattack (Claw/Claw/Bite)
* Poison (Bite)
* Improved Grab (Bite)
* Swallow Whole
* Speed 40-ish
* Huge size, appropriate damage on natural attacks

Okay, thankfully the DMG is fairly straightforward on how this'd work. A CR 9 creature will:

have +4 proficiency bonus
have approximately 16 AC
have +7 attack bonus
Around 200 hit points
have Save DC of 16
deal 57-62 damage per turn, on average
a swallowed creature is assumed to be dealt damage for 2 rounds
d12 hit die (as it is huge)

I'll also reference another CR9 Construct - the Clay golem

So lets build a Horseless Mantispider

200 hit points with a hit die of d12... that's going to look like 16d12+96, with a Con Mod of +6
You want 3 attacks in the multiattack - two claws and a bite. An Average of 60 damage per round, makes it going to look close to 20 damage per attack. In general, bite attacks deal more damage than claws. So lets break it into 17, 17, 26.
With a prof bonus of +4, and an attack mod of +7 the monster will have a +3 to it's damage-based stat. Since we're eating things, I'll put it in strength. 4d6+3 gives us an average of 17, so that's a claw attack.
You said you wanted the bite to also inflict poison damage, so we can split up the damage. 1d12+3 piercing damage is an average of 9, and 3d10 poison damage is an average of 17, together making 26.
We can then note that our reference constructs have 3 normal features - Magic Resistance, Immutable form, and Magic Weapons. While the latter two do not impact the creature's stats, Magic Resistance is an effective AC increase of 2.


Put this all together and you get

Nightmare Fuel
CR 9 Huge Construct
HP: 200 (16d12+96)
AC 14
Speed 40 ft
STR 17 (+3)
DEX 9 (-1)
CON 22 (+6)
INT 8
WIS 8
CHA 12
Senses: Darkvision 60 Passive Perception 9
Skills: Intimidation +5
Damage Resistance: bludgeoning, piercing, and slashing from nonmagical weapons that aren't adamantine
Damage Immunities: poison, psychic
Condition Immunities: charmed, exhaustion, frightened, paralyzed, petrified, poisoned

Immutable Form. This creature is immune to any spell or effect that would alter its form.
Magic Resistance. This creature has advantage on saving throws against spells and other magical effects.
Magic Weapons. This creature's weapon attacks are magical.
Spider Climb. This creature can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Actions
Multiattack. This creature makes three attacks - two with its claws, one with its bite. If it has a creature grappled, it can replace a bite attack with a Swallow.
Claw. Melee, +7 to hit, single target within 10 ft. Hit: 17 (4d6+3) slashing damage
Bite. Melee, +7 to hit, single target within 5 ft. Hit: 9 (1d12 + 3) piercing damage and 17 (3d10) poison damage and is grappled (Escape DC 16). Until this grapple ends, the target is restrained, and the creature can't bite another target.
Swallow. A Medium or smaller target it is grappling must succeed on a DC 16 Constitution Save or become swallowed, and the grapple ends. The swallowed target is blinded and restrained, it has total cover against attacks and other effects outside the creature, and it takes 17 (3d6) poison damage at the start of each of the creature's turns. The creature can have only one target swallowed at a time.
If the creature dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 5 feet of movement, exiting prone.

[sabelo2000]

Ok wow that's awesome, it just seems so weird to me that this edition reverse-engineers monsters from CR backward, no wonder I was having so much trouble . Thank you so much for that!

[Vogie]

Ok wow that's awesome, it just seems so weird to me that this edition reverse-engineers monsters from CR backward, no wonder I was having so much trouble . Thank you so much for that!

Not necessarily. You can base it on anything you want - an ability, a weapon, an amount of damage, a certain number of hit points, or, my favorite, a cool mechanic. Then back into the stats from that point.

[Lupine]

Vogie got it mostly right, but I think Acid would probably be a better pick for the “swallow” damage, rather than poison. Just thinking that stomach acid doesn’t deal damage by any of the typical “poisons” that we see other creatures use, but rather by digesting the body.