Roleplaying games have a long history of specific damage types being more or less effective against different creatures.

I understand the narrative nature of the Genesys system eschewing many of these fiddly bits for the sake of simplicity, however damage types and immunity/resistance/vulnerability is still part of many genres: Skeletons are resistant to piercing damage, undead are vulnerable to a divine/holy elemental. Elemental creatures made from, thus immune, to one type of energy, while completely wrecked by its opposite.

Fellow GMs and setting creators, how will you, if you plan to, handle this?

I have some ideas of how I plan on handling this.

Current D&D has a good approach on damage. Loosely define some damage types, and then there are four states of damage variation: Immune, take no damage from that damage type. Resistant, take half damage (probably round down) from that damage type. Vulnerable, take double damage from that damage type. Null state, damage is applied normally. I can see myself using this approach since it's intuitive and requires very little bookkeeping on my part, other than knowing what damage a type is and whether or not the target has any sort of modifier against it.

Another way, instead of damage x0, x½, or x2, could grant additional defense or soak vs. a damage type. In a Modern setting where things like Bulletproof vests, or even Firefighter gear could easily represent a damage resistance to certain types of damage. A firefighter in full firefighter gear might have an additional soak against fire damage. So when they charge into a burning building to save someone they'd be more protected against fire specifically, but wouldn't be any more or less protected than normal against the rubble falling on them.

If a creature is vulnerable to something, like silver, maybe you could apply Breach 1 to any attack made against it with a silver weapon.

What I would suggest is to play around with soak.

Vulnerability decreases soak by 3. Resistance increases soak by 3. Immunity means you ignore that damage type.

I went with 3 because it's the high end of the suggested soak bonus for armour.

Or, if you prefer a bit more dice rolling, have vulnerability add 2 boost dice to the attack, and resistance add 2 setback dice. This treats it more like defence. See page 198 for why defence is better than a set soak bonus; apply the reverse to vulnerability.

12 minutes ago, c__beck said:

Or, if you prefer a bit more dice rolling, have vulnerability add 2 boost dice to the attack, and resistance add 2 setback dice. This treats it more like defence. See page 198 for why defence is better than a set soak bonus; apply the reverse to vulnerability.

Things might get complicated when Blast.

Vulnerability might also show in different qualities: Burn, Concussive, Disorient, Vicious.

The only kind of vulnerability I found is in the GenCon adventure. Our vampire Lady Eliza Farrow ails from sunlight sensitivity:

Quote

Sunlight Sensitivity (While exposed to sunlight, Eliza
Farrow reduces all her characteristics by 2 and halves her
Wound Threshold and Strain Threshold.)

I guess @Doughnut 's approach fits quite nicely. Vulnerabilities double damage and resistances halve damage (before soak is applied).

18 minutes ago, Grimmerling said:

Things might get complicated when Blast.

Vulnerability might also show in different qualities: Burn, Concussive, Disorient, Vicious.

Good point. I honestly think adjusting soak is going to be the best option. With WT not getting to be higher than 20 on the outside, I fear that doubling damage would cause too much trouble.

With the average WT being in the 13–15 range, doubling even a 6 damage attack could one-hit TKO. A change of 3, either way, is still a substantial adjustment.

If it's needing addressing at a table I'd just do arithmetic on stats. Resistance = 50% of damage inflicted, vulnerability = x2. I wouldn't monkey with stats and effx n such.

Boosts and Setbacks are nice narrative ways of doing it. (It was previously mentioned but I wanted to provide my own thoughts)

"Your fire splashes off of the monster and it sends shivers up your spine as it steps through the flames" [Take 2 strain from the extra threat]

or

"The fire scorches the plant causing it to convulse in pain. This gives Jenny time to move into position." [Gives a boost to Jenny for her attack]

Soak is easy but if enemies with this kind of resistance are rare then the resistances might want a more narrative focus.

I was bouncing around different ideas, then came across the stats for the Weird War setting's Occult Commando:

Quote

Arcane Weakness : Silver, blessed, or holy weapons and ammunition count their Crit Rating as 1 when used against this character.

Nice and simple. Since my campaign has werewolves and vampires, I also gave silver items the Burn 1 quality against them for a little extra oomph.

14 hours ago, 2P51 said:

If it's needing addressing at a table I'd just do arithmetic on stats. Resistance = 50% of damage inflicted, vulnerability = x2. I wouldn't monkey with stats and effx n such.

This.