I was looking at this map and realized I have a problem understanding stealth.

The guys indicated with letters are ambushing. Does that mean that they're using active stealth against passive perception? Do they get any extra bonuses to stealth check? But even if they succeed, stealth doesn't work if you don't have concealment. When the PCs move down the road and past the first stones the two D's in the bushes should be revealed, even if they're hidden. Is that right?

So, my main question is: Is there any way for ambushing creatures to wait until PCs pass them and then attack from behind?


First off, that map is infamous in my gaming group. It's from "Keep on the Shadowfell," an adventure published before even the 4e PHB. As such, it's got a lot of... quirks, and then the Stealth rules changed in the PHB2 (see Sage's link at the bottom for full details of current rules). The party is supposed to enter from the West (left) and so the kobolds are hiding on the wrong side of the bushes. There are other problems with it too, as we'll see.

I'm using the DDI Compendium glossary for reference:

  • Yes, Stealth is an active check against passive Perception.
  • They should not get any bonuses to Stealth checks. Total cover and superior concealment allow Stealth checks, and that's enough.
  • You need total concealment or superior cover to make a Stealth check. The boulders provide superior cover, but the bushes in that encounter "are lightly obscured and provide normal cover," which means that technically the kobolds not next to rocks shouldn't be able to hide at all.


Keep out of Sight: If the creature no longer has any cover or concealment from a target, it doesn’t remain hidden from the target. The creature doesn’t need superior cover, total concealment, or to stay outside line of sight, but it at least needs partial cover or partial concealment from a target to remain hidden. A hidden creature can’t use another creature as cover to remain hidden.

So once the kobolds manage to hide (somehow) then they can stay hidden by moving into squares filled with bushes.

Here's how I think it should play out: the kobolds hide before the PCs come around the bend (are placed on the map), which means they had total concealment from the PCs, allowing the Stealth checks. Then they should jump into the bushes to be able to remain hidden until the PCs are in position.

Sage's Edit: Stealth is complicated enough that it has its own stickied guide at the official 4e rules Q&A forum.

  • \$\begingroup\$ Great, thank you, that's exactly what I needed :) \$\endgroup\$
    – ahiskali
    Dec 12 '12 at 12:50
  • 2
    \$\begingroup\$ Glad to be of help! Wizards' adventures are full of weird stuff like that. Personally, I played it as "those dumb kobolds" and we all had a good laugh in our first session. \$\endgroup\$
    – BESW
    Dec 12 '12 at 12:51
  • \$\begingroup\$ @BESW should be noted that this map was long before the errata on stealth. In the initial version they could have hidden against a DM set DC, no mention of passive perception was made. \$\endgroup\$
    – wax eagle
    Dec 12 '12 at 15:22

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