In The Spire of Long Shadows, there's a part early on in the adventure where some barbed devils and a quartet of bone devils show up to attack the party; the party has a fragment of the rod of seven parts, which they really want for some reason.
I remembered reading in one of the Planescape monster manuals that bone devils, aka osyluths, were basically devil police for the Nine Hells. 3rd Edition gives them a similar role, so it seemed odd that they were getting bossed around by barbed devils.
But then this was a 3rd Edition adventure: what with all the numbers scaling maybe they were the only devil you could throw at the party without maybe making things too easy or hard (because 3rd Edition used the wonky Challenge Rating system that was rarely accurate).
Really though if the current party didn't have a cambion, and that cambion didn't already have to deal with infernal siblings trying to get their claws on the rod fragment, I probably wouldn't even include them at all, but at least this way it kind of makes sense.
This meant I'd have to convert them, and while converting the bone devil to Dungeons & Delvers: Black Book I decided to check out what it could do across various editions. Here's what I found.
This was back when bone devils were referred to as osyluths. They were described as the "police officers" of Baator (aka the Nine Hells), and looked like a rail thin husk of a human, tightly covered in skin, with a scorpion-like tail. Aside from pit fiends, they could punish any baatezu by sending them into the Pit of Flame for 101 days.
They'd also get together to help vote on which gelugons (ie, ice devils) to promote to pit fiend status, and after a set period of time every osyluth would get automatically promoted to hamatula (ie, barbed devil) status, though sometimes one gets turned into an amnizu (ie, Styx devil) instead.
Mechanically, osyluths weighed in at 5 Hit Dice (or 22.5 hp on average), AC 3 (effectively 17 in later editions), effectively +5 to hit, and a claw, claw, bite, and stinger routine. The claws only inflicted a meager 1d4 damage each, while the bite was a bit better though still pretty sad at 1d8 damage. The stinger dealt a pretty good 3d4 damage and injected a poison that caused victims to lose 1d4 Strength for 1d10 rounds.
Their unique magical abilities allowed them to fly, turn invisible, and conjure a wall of ice (this was in addition to the generic devil magic such as animate dead, charm person, know alignment, and teleport without error). They could also use improved phantasmal force, though I don't know what it does, and were surrounded by a constant 5-foot aura of fear.
So, lotta stuff to juggle, most of which wouldn't get used anyway.
Here they're referred to as both bone devils and osyluths. They're considerably beefed up, having 10 Hit Dice, plus an additional 50 due to their whopping Constitution of 21 (which grants +5 hit points per Hit Die), giving them an average hp total of 95.
Their AC gets catapulted to 25, their attacks get either a +14 or +12 to hit, though their damage doesn't see much of an increase: the damage dice remains the same, but they get a bonus from their Strength (which like Constitution also confers a +5 bonus to attack and damage rolls).
The spell list gets mercifully trimmed to greater teleport, dimensional anchor, fly, invisibility, major image, and again wall of ice for some reason.
As in 2nd Edition they're still devil police, but they also act as informers. No mention of being able to send other devils to the Pit of Flame: presumably they need to report to a higher up devil so they can mete out punishment.
3rd Edition has a lot of assumed math, so the ramped up numbers makes sense in that context (though if there wasn't a lot of assumed math the numbers would have to get so insane in the first place). I do like that there are fewer spells, though only a few really make sense for spying on and possibly detaining creatures.
Hit Dice are ramped up yet again (to 15), though their Strength and Constitution scores are reduced by 2-3 points (giving them +4's instead of +5's). They have wings but no magical powers of any sort (not even as an optional thing in a sidebar). Bite attack is gone, but their claws now deal a base 1d8 damage.
Flavor-wise they no longer enforce the laws of hell. Instead they make other devils to do whatever work needs to be done in the Nine Hells.
Overall simpler, but boring: they're basically spiky Large humanoids with flight and a poison attack.
Dungeons & Delvers: Black Book
Personally I like the Tony DiTerlizzi art (which I used above): the 5th Edition bone devil just looks over the top, like they figured piling on more spikes makes it scarier or something. So I'm going with a more classic look.
For its Level (effectively Hit Dice) I just met in the middle at 10. There isn't a lot of scaling numbers in Black Book anyway: we've run playtests where low level characters managed to take out single monsters 5 or so levels higher than they were (albeit with some lucky rolls).
I'm sticking with the Hell police angle, so they'll need good Insight and Perception, and invisibility will make it even easier to monitor and sneak up on offenders. A fear aura plus a high Intimidate modifier makes sense for making creatures back down or confess their crimes.
I didn't want to give them the ability to conjure walls of ice, because it doesn't really make sense, though being able to summon a wall would handy for blocking an exit, or even encasing a creature completely. Since they're called bone devils I let them instead summon a wall of bone (freakier than a wall of ice, though I could also see them summoning cage walls or even just cages to trap creatures).
Since I wanted them to do more weird shit with bones, I also gave them the ability to just touch a creature and break its arms, legs, or even ribs: in any case it's also good for keeping creatures from running or fighting back.
The stinger is still there, but the poison messes with a creature's bones, draining their Constitution (which has the added effect of making them more susceptible to its other abilities and future poison attempts): if your Constitution gets reduced to -5, you're bones are completely dissolved and you just die.
Here's the finished bone devil:
Level 10 Large Demon
Speed 40 feet; flying (magical)
STR +5 DEX +3 WIS +2
CON +4 INT +2 CHA +3
Intimidate +7, Insight +6, Perception +6
AC 16 DR 3
Fort +4 Ref +3 Will +5
Immune charm (so you can just enchant your way out of trouble), fire, poison
Vulnerable silver and magic weapons ignore the bone devil’s DR, and silver weapons deal +1d6 damage (making silver really useful against them)
Wounds 80 Vitality 30 Total 110
- Multiattack the bone devil makes two claw attacks and a sting attack.
- Claw +9 to hit; 1d8+9 slashing damage (armor piercing 1)
- Sting +9 to hit; 1d10+0 piercing damage (armor piercing 3); if this inflicts WP damage the target suffers an additional 3d6+8 poison damage and has their Constitution reduced by 1 (DC 18 Fortitude save for half damage and no Constitution reduction) as their very bones start to soften and deteriorate. If a creature's Constitution is reduced to -5, its bones are completely dissolved and it instead dies.
Spell-Like Abilities (Recharge 5+)
When the bone devil uses one of these it cannot use any of them until it recharges (makes more sense for a creature with magical reserves, as opposed to being able to use various abilities x number of times per day).
- Bonesnap Must touch a creature. Suffers 7d6+6 damage (ignores armor) and a limb is broken (-2 to activities that benefit from having both limbs; can break ribs to make the target slowed but can suffer 1d8 damage to move full Speed for a round). DC 16 Fortitude save means half damage and limb is only fractured (-1 until healed).
- Improved Invisibility Turns invisible, and can attack but remains invisible. Lasts 10 rounds.
- Wall of Bone Covers 10 5-foot spaces. Each section has 75 hp (takes +5 damage from blunt weapons). Can also create a ceiling. Bones molder and rot away after 10 minutes.
- Fear Aura Creatures adjacent to a bone devil are automatically frightened (-2 to all d20 rolls) unless they're 10th-level or higher.
- Invisibility Standard Action. Lasts 10 minutes or until the bone devil attacks or uses an offensive spell.
If you want to be particularly vicious, you could give them basically a save or die ability that causes a creature's skeleton to completely burst forth from its body. I considered giving it an ability that makes bone spurs explode from a creature, or even just tear bones right out of you (like on a critical hit), but figured it has enough going on already: I'll just add them as optional powers that bump up its XP value.
After putting it to a vote, the next couple of classes on the docket are the warden (think 4E D&D warden) and apothecary (gotta go see what they're all about).
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