flotsam and jetsam for tabletop games, by quadra.

Challenge HP for Mothership

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You know the scene: the heroes are trying to accomplish something…and they need more time that they just don’t have. One hacker watches the guards’ flashlights swinging through the office as the other types frantically at the terminal: the decryption progress bar creeps towards 100%, all too slowly. The teamsters cringe as they hear the alien smash into room after room, getting closer and closer as they frantically try to pry the blast door open just a little further…

In Mothership, player characters start out pretty bad at doing most things, with an approximately 1-in-3 chance of accomplishing any task they don’t have a skill in. This can help create something like these tense scenes, but it’ll be more like characters repeatedly fumbling in desperation, failing to find purchase in the door, trying random passwords until they find one that works, etc. This works well for a horror game with low-level characters. But for more seasoned, higher-level characters, who can more reliably hack, jury-rig, repair, pry, and crack — or for tasks that are not especially difficult but simply take time — we can add HP to the task itself to add a sense of progression.

Thanks to Index Card RPG for the inspiration!

Challenge HP Tasks

The idea is simple: give certain tasks 100 HP that players must whittle down to complete by performing actions that would help complete the task. The players must always declare new actions — taking the same action twice will have no further effect. If the task in its current state requires no special skills, they simply make a d100 roll and subtract the result from the task HP. If the task does require special skills, they make an attribute roll, and subtract the result from the task HP if they succeed.

The type of action needed to progress can change depending on the situation and actions the players have taken:

Warden: You hear the heavy footsteps booming down the hallway. There’s a blast door between you and the outside, but it’s shut. What do you do?

Raza: I use my crowbar to try and pry it open!

Warden: OK — this is a big heavy door, so we’re using Challenge HP for this. Roll Strength to try and pry the door open.

Raza: Alright — Nice, success! I got a 34, under my 50 Strength.

Warden: OK great. As the steps get louder and louder, you manage to use the crowbar to wedge the door open. It’s about a third of the way to being open enough for you to get through.

Raza: Nice! Can I use my crowbar again to open it wider?

Warden: No, that 34 is all you can get out of the crowbar for this task. But since you did the hard part already — just getting the shut door to open a bit — now all you need to do is pull it open, so for any actions you take to do that, you’ll just be making straight d100 rolls and knocking the result off of the Challenge HP.

Raza: Oh cool, I’ll just put my shoulder into it and heave! [Rolls] OK, shoot, I got a 62! So close!

Warden: Yep, you get the door almost open enough for you to squeeze through it — you’re at 96%! But the beast is in sight now and charging at you! What do you do?

Examples of unskilled actions:

Examples of skilled actions:

Straight d100 Rolls (0-99) 1 2 3 4 5 6+
Probability of completing the task 0% 51% 84% 96% 99% >99%

Using 100 HP for the task is nice because it’s easy to remember, you can easily tell players their progress as a percentage, and the task will always take a few rounds to complete. But you can always use higher or lower numbers for easier or harder tasks, respectively.

Also, feel free to adjust with advantage and disadvantage to further represent difficulty. Allow players to assist each other or find clever ways to allow them to make the roll with advantage, if it makes sense (someone helping pull wreckage out of a hallway makes sense, two people typing on the same keyboard to hack faster does not).

Use this technique sparingly, and only for situations where it makes sense for the task to require progress and there’s a time pressure. Be transparent about how it works, and tell your players their progress as they go.

Contests with Challenge HP

If your players find themselves in the desperate situation of building a barricade using debris while monsters are trying to get through or something similar, you can turn the task into a contest using challenge HP: PCs advance their goal by rolling and the monsters roll to tear it down. At the end of each round, adjust the totals, adding the PC rolls and subtracting the monster rolls. If at the end of a round the challenge HP is 0%, the door flies open, the barricade breaks, etc. If it reaches 100%, they shut the door, the barricade holds, etc. The monsters can still try to break through, but downgrade their roll to use disadvantage. This will buy the PCs some time to make their escape.

Example: Smith is barricading a door as a monster is pushing its way in and Astrid is trying to find another way out. Smith rolls a 32 but the monster rolls a 31. Seeing that the barricade is only at 1%, Astrid runs back to help. In the next round, they both roll, Smith rolling a 15 and Astrid rolling a 63. The monsters only roll a 9. The barricade’s looking good now, at 55% (1+63-9). Astrid and Smith keep building up the barricade, and this time their highest roll is an 89! The barricade reaches 100% and the monster must now roll with disadvantage each round until it reaches 0% and they’ve torn it down.

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