[RPG] How do vulnerabilities combine, when taking multiple types of damage

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When a creature has multiple vulnerabilities, and is hit by an attack that deals more than one type of damage that it is vulnerable to, do the vulnerability effects combine?

Example 1: Creature is Vulnerable 5 Thunder and Vulnerable 2 Lightning. Attack deals Thunder and Lightning damage. Does the creature take 7 extra damage?

Example 2: Creature is subjected to a single effect that deals ongoing Fire and Radiant damage, while it is Vulnerable 5 All. Does the creature take 10 extra damage, when taking the ongoing damage?

Best Answer

If I'm not mistaken, your Example 2 actually encompasses two different cases, so I'm restating your examples and breaking out my answers accordingly:

Example 1: Creature is Vulnerable 5 Thunder and Vulnerable 2 Lightning. [A single] Attack deals Thunder and Lightning damage.

Example 2a: Creature is affected by [A single effect dealing] Ongoing Fire & Radiant 5, while it is Vulnerable 5 All.

Example 2b: Creature is affected by [two separate effects dealing] Ongoing Fire 5 and Ongoing Radiant 5, while it is Vulnerable 5 All.

Which should result in the following rulings:

Outcome 1: 7 extra damage.
Outcome 2a: 5 extra damage.
Outcome 2b: 10 extra damage.

Assumptions:

  • "Vuln [type] [#]" means "whenever the creature suffers a hit of damage type [type], the creature takes [#] extra points of damage."
  • Whenever a creature suffers a discrete incident of damage, evaluate that damage in isolation against all the creature's vulnerabilities, resistances, triggering effects, etc. etc.
  • If a single damaging effect has two types, all points of damage are considered simultaneously to be of both types; 5 fire&radiant is not 2.5 fire / 2.5 radiant, and thus is not two separate 'hits.'

Conclusions:

  • In example 1, the creature suffers a single instance of damage which just happens to deal Thunder and Lightning damage. Evaluate the hit against all the creature's vulnerabilities:
    1. The creature's Vuln 5 Thunder triggers (since the damage is typed Thunder, it meets the criteria for this vulnerability).
    2. The creature's Vuln 2 Lightning triggers (also meets the criteria for this vulnerability).
  • In example 2a, the creature suffers a single instance of damage which just happens to count as both Fire and Radiant simultaneously. Therefore the "Vulnerable 5 All" gets triggered once (the typing of the damage [Fire&Radiant] meets the criteria for the vulnerability).
  • In example 2b, the creature suffers a separate instance of Fire damage and Radiant damage - two separate "hits" trigger the Vulnerable rules two separate times, exactly as if two separate instances of example 2a had occurred.
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