D&D 5E (+)Heat, a New Mechanic For Managing Power Systems

[doctorbadwolf]

This is an idea I originally had for some experimental 2-person air vehicles made by the wealthy artificer the group is friends with in my Eberron game, and I'm going to expand on in my more crystalpunk homebrew settings.

The basic idea is very simple.

A device, vehicle, weapon, etc, has a Heat Die, which represents it's capacity for rapid or prolonged or intense use. The higher the Die, the higher the capacity.
eg, the arcane impulse thrusters of a slicer, a small 2 person flying machine with 3 guns and a small but powerful engine, steered with the use of pilot-controlled "wing-sails" and tiny maneuvering thrusters, has a d8 heat die, it's two light guns have a d6 each, and the big pilot gun has a d4.

Normal usage generally doesn't require a roll of the Heat Die, but when you push the system, overcharge a weapon, or maintain maximum usage beyond a very short span, you roll. Your Heat generally starts at 1, which means as long as you don't roll a 1, nothing happens. If you do roll a 1, your Heat increases by 1 point, to 2. Now you have to roll higher than two to avoid the device heating up.

Not using the system for a round drops Heat by 1, and you can spend a bonus action to attempt to reduce heat, or taking an action to automatically succeed at doing so, by 1 point.

You might also allow dangerous maneuvers like venting heat from one system to overcharge another, with degrees of success determining how much extra juice you get in the target system, and whether you reduce, maintain, or increase, the source system's heat.

When heat is maxed out on the die, you suffer a mishap, and the system's is volatile until repaired. An volatile system, even once it get it working again in the short term, starts back at 2 rather than 1, and whenever you roll Heat, you roll two dice and use the lower result.

You can increase the capacity of a system by connecting it to a larger system or upgrading it with an expanded capacitor. Such a system rolls Heat twice, and uses the higher result, once per round.


In Space Fantasy!, there are energised melee weapons with heat dice, devices that allow you to transfer heat from a device or system to an enemy system, if they fail a save, dealing damage and forcing them to make heat rolls, etc. I'm thinking of upping the damage dealt by most characters by having energy weapons all have an extra damage die, and a heat die that is rolled any time you use the extra damage die, but that might suck in play.

Remember that it's a (+) thread, so no thread crapping, don't try to tell me that my whole premised is dumb and I should feel bad, etc.

I'm also toying with the idea of giving complex devices, upgradable weapons, and vehicles, all infusion slots, allowing for upgrades to that item. A bit Final Fantasy 7, a bit Star Wars.

Just thought it might be fun to share, let me know what you think? Would you use something like this in a magitech setting? What about in a sci-fi game? Any pitfalls that seem obvious to you that I seem to have missed?

 

[MarkB]

Neat idea. One option I'd suggest is allowing a player to increase Heat automatically (without rolling) in order to provide an improved result, such as increased damage on an attack, or greater speed / agility from a vehicle. Only allow it if the increase wouldn't result in a mishap (because at that point their chances of rolling a success are slim enough that there's practically no downside). For the increased damage example, let them choose the option after they know the attack has hit.

 

[doctorbadwolf]

Other things that exist alongside this idea.

Ship Roles and Proficiencies
Each role has stuff you can do as one of the ship's actions, in addition to your own turn, when filling that role. Captain isn't listed because it isn't a role with mechanical weight, it's just a social position of command on the ship, and a PC ship might not even have one.

Also, each role has responsibilities that are called upon when rolling for hazards in a journey, using rules very similar to Adventures In Middle Earth. When you purview is challenged by a hazard, you are in change of the scene to resolve it.

 

[doctorbadwolf]

Neat idea. One option I'd suggest is allowing a player to increase Heat automatically (without rolling) in order to provide an improved result, such as increased damage on an attack, or greater speed / agility from a vehicle. Only allow it if the increase wouldn't result in a mishap (because at that point their chances of rolling a success are slim enough that there's practically no downside). For the increased damage example, let them choose the option after they know the attack has hit.

Hell yeah! I love that. Probably get more out of the action if you choose to simply increase heat, vs rolling for it.

So, to increase damage, lets say that we are doing a 3 stage success ladder with 1 stage of total failure.

Fail - 1-8 - nothing happens but you still roll for heat
Minor Failure 9-12 - Nothing happens, no heat roll
Minor Success 13 - 19 - gain 1d10 extra force damage, roll for heat
Total success 20+ - Gain 2d6 extra force damage, roll for heat?
Push it! - Choose to increase heat without rolling when you gain any success - add an additional 2d6 force damage.

Something like that. Could be simpler, obviously. Making it semi-binary would give a DC, pass or fail. Fail becomes Minor Failure (only roll for heat if it fails and you roll a nat 1. high enough skill would mean this becomes impossible for, say, a high level rogue), success becomes Minor Success, and success with a nat 20 becomes total success.

Also appropriate damage depends on level, so perhaps there are simple damage upgrades for ships, or characters of different tiers add more or less to damage when boosting damage?

 

[Fanaelialae]

I like it! You could also offer options for an increased risk/reward.

For example, firing a plasma rifle would require a heat check as normal. But firing it in burst mode could require a heat check at a -1 or -2 penalty.

I could also see a magic system built around this mechanic. In a psionics system based on this, psions might risk losing control and going Akira if they overuse their powers.

 

[doctorbadwolf]

I like it! You could also offer options for an increased risk/reward.

For example, firing a plasma rifle would require a heat check as normal. But firing it in burst mode could require a heat check at a -1 or -2 penalty.

I could also see a magic system built around this mechanic. In a psionics system based on this, psions might risk losing control and going Akira if they overuse their powers.

Yeah! I was actually thinking about that earlier while reading about @Morrus post about the psion for the level up scifi book.

I actually would love an alternate magic system that used magic skills and your level of training gives you a bigger die, with burning out and needing to rest to use that skill again as a risk of overuse.

I could even see a way to incorporate spells as ritualised advanced uses of skills that you can learn but don't gain any automatically, necessarily, and a system of capacity alongside the die that determines how much power you can channel, possibly even allowing the ability to overcharge and punch above your powerlevel at the risk of automatic burnout and physical/spiritual damage to yourself.

Another way to go, for anyone not wanting to rewrite magic in dnd lol is to base an artificer subclass or even a variant base artificer class on this mechanic.

 

[MarkB]

One thing I was considering was, instead of increasing the failure threshold above 1 each time you build heat, you could drop the die size you roll by 1. Maybe include 1d3 and 1d2 (coin-flip) for greater range.

 

[Charlaquin]

Neat! I’d want to see it in play, because on paper it seems like it could take a lot of uses before heat builds up enough to be of any real concern. But generally I like it.

 

[doctorbadwolf]

One thing I was considering was, instead of increasing the failure threshold above 1 each time you build heat, you could drop the die size you roll by 1. Maybe include 1d3 and 1d2 (coin-flip) for greater range.

I really enjoyed the sense of building tension that came from the threshold going up. Especially because I had them stack counters to track their current Heat.

Another way to build heat might be to roll more dice, and any 1 increases Heat. So if you get a 1, you now have 2 heat and roll 2d6. If either of those gets a 1, increase heat to 3 and roll 3d6 next time, etc.

 

[payn]

Im getting Battletech vibes here. Maybe that system can give some ideas on how to expand on this? Having to manage heat round by round and decide on movement (walk, run, jump jet) and which of your weapons to use was very tactical. Doesnt feel the same every round either.