Halloween in the Deep Carbon Observatory: a Challenge, a Session, a Debriefing

First: 

This is not a review. I like Deep Carbon Observatory a lot, and I recommend it if you don't have it. Most of the evaluation bits of this post focus on stuff that went wrong with the module rather than stuff that went right; that’s more due to what I tried to do with it than the quality of the thing itself. This post is more about planning out a session with DCO and reviewing what happened.

You can buy it here. The PDF is $10.00; the softcover is $13.30. 

The Setup: 

The Challenge:
I have four hours to run a Halloween oneshot for a group that normally plays combat-focused 5e. This is the opportunity to give the players a taste of wonder instead of spending four hours fighting through four rooms.

The Module:
Deep Carbon Observatory, specifically the final dungeon--the Observatory itself. It's an ancient ruin full of lethal treasure. A cruel band of NPC adventurers--the Crows--stalks the party.

The System:

You can download the version I used for the oneshot here. It's short, just 7 pages long, and covers character generation only. 

I'm working on a hack that combines Into the Odd mechanics with GLOG classes. This version is, like Into the Odd, classless, so there's way more Into than there is GLOG, but I'm going to keep working on it. The Failed Career table is based on James', and the Quirks table is a modification of one I collaborated on with the OSR Discord, which Saker Tarsos instigated and posted on his blog.

The Plan:

1. Players generate their characters. Hopefully a half hour or less. Could be ten minutes if people arrive on time. 
2. Read starting blurb about ancient kingdom with great powers, do best possible Cate Blanchett impression. 
3. The players start outside the observatory proper. They were headed to Carrowmore; it was flooded. They ventured upriver to find the source of the flood. They were not the only ones (stragglers as replacement PCs + Crows). Eventually, they arrived here: A deep, black pit, with mirrored towers surrounding it, perfectly dry. At the bottom is a gate. Cue the music. 
4. Run the observatory proper. The Last Thing is in room 39, as suggested. The Crows harass the PCs and try to steal their stuff. Hopefully they release the Last Thing and die horribly. 
5. In the event of TPK before session end: Run Isles of the Dead (this step is implicit in all my sessions). 
6. In the event that the players actually survive the Observatory and lose the Crows and the Last Thing, they can venture toward Carrowmore. 

They are not as spooky if you kill their friends before meeting them (Scrap Princess)

The Crows: 
Hooloch can reload and fire on the same turn and gets two melee attacks. Zolushika has a derringer (d8, exploding 6-8, 1-in-6 reload, melee range, last resort). The Snakewood Staff takes 1 Max HP/use.
They arrived a few hours before the PCs, opened the gate, scouted out the first room, then left and waited for someone else to come by and venture down. They will harass with zombies and special arrows every night, or attack in the Observatory if they see an opportunity.


All of that was written before I ran the session. No plan survives contact with the players.

I don't really want to do a room-by-room session report, so just take this player map instead

The Debriefing: 

In Summary: 

1. Into the GLOG is a solid foundation
2. I’m bad at horror
3. The Observatory is not suitable for a single 4-hour Halloween Oneshot
4. All the talk of randomly generated abilities encouraging player ingenuity is absolutely correct

Self/System Evaluation: 

1. The Character Generation Packets (the Into the GLOG document above) were a resounding success. I printed out six copies and put them on the table; each player had their own. We were able to start playing in just a few minutes, and the characters were fairly interesting. The players definitely read the Player Advice page, although I don’t think they processed it fully. 
2. I’m happy with HP calibration. Monsters get HD*8 HP and each “level” of Armor grants 1 Damage Reduction (see the rules doc for player HP). Monsters felt tough without taking forever to kill, and players were clearly in danger (two died, there were a bunch of lost fingers and one lost hand) but not unfairly so. I’ve struggled with balancing monster and player toughness for the entirety of my time GMing OSR stuff (about the last year), and this system was the first to feel really good. 
3. I tried classic “both sides roll a d6, whoever rolls higher goes first” initiative, and I think I still prefer the GLOG style of “everyone rolls an initiative check; anyone who succeeds goes before the monsters.” I’m already fairly lenient in terms of allowing players to ambush things, so having every player act at once even in regular combat is too swingy for my tastes.  
4. I don’t really know how to handle players asking to attack things outside of combat yet. I had them just roll for damage like regular Oddomatic attacks, which worked out okay, but didn’t feel great. I probably should have allowed the players to just execute the guy in the Razored Lock, but I had them roll for damage twice instead, which was weird. Screwing with the ooze automatons led to a couple of similarly difficult rulings on “fighting without entering combat”: How do I handle the automaton grabbing for a jar out of a backpack? How about players shooting the jar out of its hands? What I did was have the player make a STR check to avoid being grabbed, and when they failed I had the automaton just take the jar out of their backpack, and that felt alright. When they wanted to shoot the jar out of its hands, I just said “you shoot it and it shatters,” but in retrospect I should have given it “Damage Reduction 3, HP 1” or something to model the automaton trying to protect it. 
5. I forgot to implement reloading for pistols, which in theory makes them a decent chunk more powerful than regular melee weapons and much stronger than bows, but in practice--in the context of a oneshot where players didn’t have the opportunity to shop--it didn’t really matter. People who started with guns used them; people who started with bows or daggers used those. 
6. I’m not confident enough in sad/scary things to run them well. Specifically, I feel awkward describing things seriously instead of in a lighthearted tone; I’m not confident in my descriptive abilities. Hopefully I'll be able to practice this and it'll help. 
7. Using a speaker for music didn’t work out very well; we were playing in a room with 5 other groups (it's a large club), so the background noise basically forced me to keep the music down in order to be heard. The playlists were also a bit short. 20 minutes of exploration music probably isn't enough. 

Cane Threadington, his argumentative tattoo of his ex-wife, and his blood, which is spiders

DCO Evaluation:

1. The Observatory itself isn’t really scary. I know that information is in the module, but I foolishly thought I could make it scary and it wasn’t. It’s a series of rooms full of great dangerous toys and NPCs, but without the context of the trip upriver and the dam and the lakebed I don’t think it had a properly eerie feel. Player feedback indicated that, too; there were a couple things that were a bit creepy, but the players mostly just attacked them. They didn't reach the Last Thing. 
2. The Observatory itself is too long to run in a oneshot, at least for me. We got a bit less than halfway through in about 3.5 hours of play. They explored most of the right stalactite, ending at the Book Elf Woman. 
3. The players killed the guy in the Razored Lock and the mushroom dudes, which may have damaged the horror feel early on. 
4. My mapping player was able to map the vertical dungeon fairly well, but I think the players' vision of the space they were in was harmed (I’m not good enough at description to improvise the horizontal layer, I don’t think). 
5. As far as I can tell, the Observatory does not/should not have random encounters. Without random encounters, I didn't think to track light-time, and without tracking light-time I didn’t think to track light-radius, which is itself made worse by DCO’s vertical map. This was a oneshot, so ultimately all of that was fine or even good, but I think it’s still important to note that all of those concepts are strongly linked. I need to consider them together in my regular campaign. 
6. My players LOVED the scales. They spent maybe about an hour real-time goofing around with them. They used them to identify ghar’s crossbow bolts, figure out their own character traits, compare how cool two PCs were (had to be settled by IRL arm wrestle), assess the magicalness/dangerousness of various objects, and probe the moral opinions of the scale (they learned that it doesn't think very highly of souls or freedom). 
7. They obsessed over the Cervit ceramic plates for a while without discovering what they actually did, and they didn't think to ask NPCs what they did. 
8. I ran the Crows in a somewhat forgiving way, since with Oddomatic attacks and a party used to direct-combat 5e the players would have just been crushed. They were able to ambush and kill Ghar and Zolushika, but the other two are still at large. The players were a little bit creeped out, but without the history of the journey upriver I don’t think the Crows were anywhere near as scary. 

Roxas Carter, Pirate King, who can mix oil and water, with an animated zombie hand taped to his right stump, wearing a crabclaw over that, wearing a shield, holding a magic arrow. There's another guy borrowing his eyepatch. And he has viking horns. And two peg legs. And a gun. Honestly, there's a lot going on here. 

Player Stuff:

1. Using the Scales to identify Ghar’s crossbow bolts. They were able to get keywords like “hallucinations,” “ensaring,” and “scrying”
2. Using the quirk “you can mix oil and water” to mix oil into the water-based automaton oozes and burn them for lots of damage
3. Ghar shot one of the players with his eyeball-seeing arrow, and then that player took another player’s eyepatch and put it over that eye for no reason in particular, allowing them to ambush the Crows. They then found the mirror, displaying fabric (they thought it was the inside of a pocket), and then later when they checked on the player’s eye I told them that the mirror was showing what he saw (over the course of a couple exchanges). They were amused that they had accidentally thwarted the spying attempt.
4. When they found the alien plant biospheres, the only player in the room said “I drop it on the ground at my feet.” 5d6 damage, Save for Half: They lived through that incident with 2 STR (and some lost fingers) but later died.
5. Welded automaton fingers to the iron palms of the person who dropped a bomb on themselves. 
6. Animated a zombie hand, tied it to the stump of another person who lost a hand, put a crabclaw on top of that, and put a shield on the whole thing
7. Two characters died during direct combat with the silk golems/silk tapestry, because they basically just traded blows and lobbed alien plant biospheres (and rolled poorly).
8. One of the players—someone new to TTRPGs—walked in like a zombie, and said “I feel like crap, guys, so I might leave early.” As the session went on, however, she perked up, and played the whole time. Furthermore, she was one of the people whose character died, and after the session was over, she said “I really liked switching characters in the middle.” The OSR Works™.

Left to right: Uliczny Magik, Sometimes Invisible Street Magician; Black Brady Barnacle Butt, Iron-Palmed Pirate (Deceased); and "Tinman" Smith, Telekinetic Forester. There were some other characters, but these are the ones with art. 

Plans for the Future:
So, this group is probably not coming back to DCO. We normally play 5e with a different DM, and we only have a few sessions left, so we're probably just going to keep playing through that campaign.

If I run DCO again in the future, I’m going to expand my music selection, run it in a quieter room, and run the entire module. If I run another Halloween oneshot, it'll probably be something campy rather than scary.

Otherwise, I’m going to keep working on Into the GLOG, write up some classes, and go back to running non-horror stuff with my regular group.

It turns out that posting weekly is too often. Things will be sporadic.  If you want to hear about stuff early, hang out on the OSR Discord.