Erestor said:
Hello
Does Vulnerability Stack ?
If I use the Feat "Lasting Frost", that give a 5 frost vulnerability and use the power of an Orb (don't remember that name) that make a "magic resistance" become a "frost vulnerability 5", does the target have a frost vulnerability of 10 ?
Sorry for my bad english ^^
Short Answer: It depends, but in that situation, no.
Longer Answer: If the vulnerabilities are to different types of damage, then yes, they "stack" in a sense. In other words, if an attack does fire and radiant damage, and the creature has Fire vuln 5 and Radiant vuln 5, then they'll take 10 extra damage.
However, vulnerabilities of the same type
do not stack. Only the highest applies. Also, the orb power you are talking about only applies to creatures that have
resistance to a certain type of damage. While a creature
can have both a resistance and vulnerability to the same type of damage, it almost never happens (never naturally). So the situation where that orb created a vulnerability to something that they were already vulnerable against is relatively unlikely, but then whichever vulnerability was higher would apply.
It's easy to know if you just look at resistances (or imagine how they work) as they follow the exact same rules. By the way, the rules on Resistances and Vulnerabilites in the PHB is on page 276. The monster manual also has a small blurb in the glossary, but it doesn't say much.
