I am currently putting together a dhampir blood hunter character and I noticed something interesting, which I would like to verify the RAW about:
The Order of the Lycan, Heightened Senses is described as:
When you choose this archetype at 3rd level, you gain the improved
senses of a natural predator. You have advantage on Wisdom
(Perception) checks that rely on hearing or smell.
The Passive Checks section in the basic rules states:
Here's how to determine a character's total for a passive check:
10 + all modifiers that normally apply to the check
If the character has advantage on the check, add 5. For disadvantage,
subtract 5. The game refers to a passive check total as a score.
And finally, the Observant feat states (third point, emphasis my own):
You have a +5 bonus to your passive Wisdom (Perception) and passive
Intelligence (Investigation) scores.
So, that would leave a Lvl 4 Dhampir Order of the Lycan Blood Hunter, proficient in Perception, 16 Wisdom, and who just took the Observant feat rocking a passive perception of:
10 + 2 (Proficiency) + 5 (Heightened Senses) + 5 (Observant) + 3 (Wisdom) for a total passive perception of 25
I know that resistances and weaknesses do double, but I am wondering if I am correct in stacking the advantages of a passive check. Do they stack, or does this break the game?
Best Answer
They stack
Fifth edition largely did away with things that don't stack with each other. If two different things both grant a bonus to something (and those bonuses are numerical - not like "Advantage" or "Resistance" which either you have or you don't) they stack unless they say they don't.
Partly because of this, first party material (items, feats, etc.) for 5e tends not to hand out many bonuses to ability checks, saving throws, and attack rolls.
In the case of passive perception, though, it would be very difficult to break the game. That would require that some aspect of the game be balanced around characters not having a high passive perception score, or perhaps have some mechanic that allows a character to leverage their passive perception score into bonuses or advantages in other situations. Neither of those things exist as mechanics. It seems to me that the designers are willing to loosen up and hand out more numerical bonuses to this particular value as a result.