Here are a set of perception rules built from a suggestion by Chris H earlier today after a Necrocarcerus session that I'm planning to put some variation of into Necrocarcerus 1.2. Perception mechanics are a good example of the kind of mechanics that should be built from the basic paradigm of a group check and then adapted to situations where individuals use them. For this reason, perception should not be a skill, but rather something made easier or harder by the number of participants.
Perception mechanics cover only situations in which PCs do not specifically describe how they are investigating an object or area.
Characters who are actively hiding may be spotted by exceeding the results of their Stealth check. Objects like hidden doors have static concealment scores.
Passive Perception Scores
Passive perception is used when characters are not actively searching. The passive perception score of a group of characters is equal to the number of them who are not distracted and are able to perceive their environment (i.e. they have adequate light).
Active Perception Checks
A group of characters makes a single active perception check whenever they search an object or area. Checks may also be used for tracking enemies.
Active perception checks involve rolling a single d6 and adding the number of characters in the group who are not distracted and able to perceive their environment to the result of the roll.
Additional Material From Elsewhere in the Necrocarcerus Document:
Only areas that are adequately lit may be actively searched. If PCs have a light source in a dark area, they may only search the area or object the light source illuminates until it is moved, using an action.
Hirelings do not normally add to perception scores or checks, though named NPC allies accompanying the party do.
As Yet Undecided:
What "Hide in Shadows" does? Three options suggest themselves, varying in power:
1) On a successful Hide in Shadows check, the character counts as having rolled the maximum possible Stealth check (based on their skill, using Skills: the Middle Road). This still incentivises them to better their Stealth check, though they would rarely roll it.
2) A successful Hide in Shadows check allows a reroll of the hiding character's Stealth check, keeping the higher result of the two.
2) On a successful Hide in Shadows check, searchers use only their passive perception for the purposes of detecting the character.
I'm open to suggestions about which to adopt.