Ways for Monsters to See in the Dark

[Farmer]

Originally Posted by ericthered

Is there a reference for seeing via ground vibrations rather than air vibrations? That's something else that might end up being ambient

"oh no, they're coming" is a fun thing to play with.

This is a very well referenced Wikipedia article on Seismic communication:

https://en.wikipedia.org/wiki/Seismic_communication

Consider that larger animals would generally mean lower frequencies, as a guide for scaling.

The classic long range one in nature that is well studied, if not completely understood from the communications perspective, is elephants, and there is plenty of scientific, academic, and general interest literature available with data and studies if you want to dig in that deep.

[Anthony]

The big problem with targeting via ground vibration is that common ground vibration has a quite large wavelength (likely multiple meters), which isn't really usable for localization unless you have extremely widely spaced sensors or the distance is very short.

[jason taylor]

Originally Posted by ericthered

I'm working on a setting/scenario where Modern-Day Folks delve into a Dungeon Fantasy style under-dark. I'm looking into what sorts of vision the monsters and local inhabitants might be using down there, and I'm trying to go beyond just "magic vision". Thoughts so far:

• Echolocation sounds really neat, and I'm leaning towards tying my goblins thematically to bats.
• Infravision seems to have the downside that it doesn't allow you to see the tunnels, and while being able to freely target in combat is nice, its also nice to see stalactites hanging at face level. Am I reading this wrong, or would cave walls be visible?
• Feeling your way through seems possible, but I'm not sure. Would four foot antanna be enough to give vibration sense? Is vibration sense a good solution for an intelligent civilization that lives in the dark.
• Magical senses sound fun, though I think making them specific to things other than "what light would hit" sounds fun. The ability to detect where air is, turned into a scanning sense, for instance?

What are some varied ways to see in the dark to populate my underdark with?

I don't know if anyone thought of this but some fish sense electricity. And fish generally have a lateral line to sense pressure and current.

[Farmer]

Originally Posted by Anthony

The big problem with targeting via ground vibration is that common ground vibration has a quite large wavelength (likely multiple meters), which isn't really usable for localization unless you have extremely widely spaced sensors or the distance is very short.

Yep. If I were creating a creature for a game, I'd probably make them a little like a submarine. Passive listening for long range and then active for short range accuracy (i.e. emit a high frequency vibration that's like echolocation but transmits through the surfaces. Their attack modes would need to reflect this (large swinging appendages or barreling charges or sticky excretions or poisonous or toxic emissions and so on. Maybe even a large enough vibration to act as a local tremor to knock foe down.

[Varyon]

Originally Posted by Farmer

Maybe even a large enough vibration to act as a local tremor to knock foe down.

I don't think you can do this natively in GURPS, but you can get really close - Innate Attack 1d cr (Area Effect, 2 yards +50%; Double Knockback +20%; Emanation -20%; No Blunt Trauma -20%; No Wounding -50%) [4/level] would result in anyone within 2 yards of the creature taking 2d worth of knockback per level, and if you get knocked back, you have to make a DX roll to stay standing (at a penalty based on how far you were knocked back). Add a Limitation that the "knockback" effect is only used to see if the character falls down (they don't actually get knocked back at all; I'd eyeball this at maybe -5%, seeing as No Knockback is -10%; making it +0% probably wouldn't be a horrible idea, honestly), and adjust Area Effect and level to taste, and you're pretty well off. Dissipation -50% might be appropriate as well, to represent the effect being less the further from the source you are (you could allow for some level of Explosion in place of Area Effect+Dissipation, although by RAW that isn't compatible with Emanation... and is honestly a pretty bad deal*).


*One level of Explosion costs the same as a 2-yard Area Effect and divides damage by 3x the distance from the epicenter - at the same 3-yard distance where the 2-yard AE terminates, you're at 1/9th damage, which is pretty weak, and I don't think getting 1/9th there, 1/12th at the next hex, and so forth is worth having 1/6th damage 2 yards away and 1/3rd 1 yard away, where AE would deal full damage. Two levels of Explosion costs the same as a 4-yard radius and divides damage by 2x the distance; at 5 yards from the target, you're at 1/10th damage. Three levels of Explosion costs the same as an 8-yard radius and divides damage by 1x the distance; at 9 yards from the target, you're at 1/9th damage. You can also compare Explosion to the above with doubled radius (4, 8, and 16, respectively) and Emanation, where Explosion is generally worse (Explosion 3 is better than Area Effect + Emanation if you deal 17 or more damage, at least). Explosion can be potentially worthwhile for some of the special effects (maximum damage for a contact explosion, triple damage for an internal one), provided you have some way to get them (and the GM lets them function this way), but those don't even apply here.

[Farmer]

Nice statting it up! I like it :-)

[Willy]

Originally Posted by Farmer

Yep. If I were creating a creature for a game, I'd probably make them a little like a submarine. Passive listening for long range and then active for short range accuracy (i.e. emit a high frequency vibration that's like echolocation but transmits through the surfaces. Their attack modes would need to reflect this (large swinging appendages or barreling charges or sticky excretions or poisonous or toxic emissions and so on. Maybe even a large enough vibration to act as a local tremor to knock foe down.

You mean like bats, their echolocation ist precise enough for any cave on this planet, maybe a parabolic hearing for passive detection combined with the bats system, Have you considered sound as a weapon? Sperm whales use it active to stun their prey.

A classic mentioned in many SF novels playing in caves are predators using a bright flash to stun or overwhelm the senses of prey. Or you use something like the black sea devil https://en.wikipedia.org/wiki/Black_seadevil to lure the prey to you.

[Farmer]

Originally Posted by Willy

You mean like bats, their echolocation ist precise enough for any cave on this planet, maybe a parabolic hearing for passive detection combined with the bats system, Have you considered sound as a weapon? Sperm whales use it active to stun their prey.

A classic mentioned in many SF novels playing in caves are predators using a bright flash to stun or overwhelm the senses of prey. Or you use something like the black sea devil https://en.wikipedia.org/wiki/Black_seadevil to lure the prey to you.

Lots of good options. It comes down to whether they are evolved to deal with sighted prey, unsighted prey, or both. And how big are they and their prey? Combination of vibration and sound is a nice one, giving long and short range options, but you could just have it one or the other. Again, it comes down to whether it makes enough sense for them to survive in the environment - excluding would be adventurers from the future/alternate world turning up and having to deal with them!

[Apollonian]

Another way, similar to IR, might be to say that the creature can detect very fine variations in the local mana field. Setting-dependent, very obviously, but if different substances (let alone different living beings) alter the way mana flows and pools through them, something's probably going to take advantage of that for sensory purposes. And spellcasting will really stand out for them.

[Anthony]

It's worth remembering that any situation in which you have substantial amounts of subterranean life implies there's an energy source down there that can support that life, and the life down there has a way of tapping into that energy source, which in turn generally means it also has the ability to detect that energy. That could in principle only be the producer organisms (subterranean equivalent of photosynthesis) but it's likely there'd be an evolutionary advantage to creatures further down the food chain also being able to detect that energy. Typically that would be magic, though other sources are possible enough.