I'm big fan of stealthy games and I like to remember about some curious cases in which character might get a bonus or penalty to stealth checks. Generally stealth and detection, different ways of percepting and hiding are one of my favourite parts of any RPG system. Here are my thoughts about it, I wonder about yours.

As gm I tell players to check stealth:

- when "sneaky" character comes into line of sight (or other sense) of the "guard" (note that it's not always because sneaker moved, the guard might have done it while sneaker is stationary)

- every time the sneaker moves while being in sense range of the guard

- every time sneaker attacks from the shadows

Here are modificators to stealth checks I use with some explanation to them.

Bonuses, or The Way of Serpent

- stationary sneakers get +20 bonus to stealth check; they have to be perfectly still to get that bonus, so no actions allowed

- sneakers in noisy place can get +10 to +30 bonus, depending on intensity of the noise

Penalties or The Way of Ox

- sneakers obscuring a light source for an enemy get -10 penalty to stealth check

- sneakers casting their shadows into enemy's line of sight get -10 penalty to stealth check

- when sneaker approaches the guard with decent smell downwind he gets -20 penalty to check

To each their own.

The numbers are essentially the same; but the mechanic as I understand it is the sneakee (is that a word?) makes an opposed awareness check with the sneaker's stealth.

The difficulty of the stealth check would be anything from trivial to challenging based on factors like background noise and so on.

The way I use it is I think of it like Dishonored.

Basically, if you are going to cross an enemy LOS in a stealth situation you make a roll. This is modified by the conditions and enemy gear.

X -----> X

-------- ----------

G

The biggest reason stealth is kind of a dump stat in Dark Heresy has to do with an unclear presentation of the map. If you design your maps around a stealth option, then people may use it.

Which is why I tend to draw out my maps. Though, my group definitely doesn't consider Stealth something to dump; one person has it maxed, another has it at +20, and everyone else has it trained or at +10. That said, they love ambushes.

It doesn't even necessarily need a detailed map. As long as the terrain is described and it's something more interesting than 'open space' stealth is always an option.

I'd concur with ambushes being the key - the first time players find themselves getting hit whilst unaware and suffer the "+30 to hit and can't dodge" from people who've had a chance to full-action aim with accurate weapons, they tend to learn substantial respect for stealth and awareness as key skills.

The biggest reason stealth is kind of a dump stat in Dark Heresy has to do with an unclear presentation of the map.

Or is it to do with how often player have to make a stealth roll ?

The more the GM makes the player roll stealth, the harder stealth becomes because whoever they are sneaking past only needs to succeed once. Lets say that a PC has a 50% chance to succeed in the stealth roll. If there are two checks, the chance of passing both is 25%, 3 is 12.5%, 4 is 6.25. That's the kind of math that makes everyone regret putting points into stealth.