Celebrim
Legend
Encounter Example 1: Bandit Attack
Party comes upon a group of 13 CR 1/2 bandits, 1 CR 8 Fighter/Rogue, 1 CR 8 Cleric, and 1 CR 8 Wizard. (According to the Encounter Calculator, that's a Deadly encounter at 23 Challenge Rating.) The party was moving silently and taking cover, approaching the bandit camp. On one side of the road were 7 bandits and the Fighter/Rogue captain; the other side was the wizard, cleric, and 6 additional bandits.
OK fine. We know the party is over geared, over-powered, under challenged and exists in strength greater than the 4 presumed characters. The above fight barely looks challenging to me even before we are talking about a strong party. It's also set up completely to favor the players.
Let's redo this. Add to the above an addition 13 CR 1/2 bandits as well as 6 CR 1/2 dogs.
The bandits additionally have a wagon with four horses that serves their logistics. The bandits camp behind a screen of heavy brush and young pine trees in a circle about 80 feet in diameter. You can see the lights of three campfires and hear them from about three times that, but not clearly enough to make out details. You can't see any campfire circle from the vantage of the road until you enter the camp. At all times, about 1/3rd of the bandits (10) are acting as sentries ringing the encampment at a distance of about 60 feet. Four of them are posted concealed in tall trees in a ring around the camp and have good vision both around them and into the camp, while four others have hides hidden in the brush, while two watch the road from a carefully constructed blind/ that gives them 90% cover and concealment. Sentries have horns as well as weapons and can give an alarm. Additionally, the bandits have constructed a variety of simple traps (bear traps, and the like) on the likely approaches to their encampment (as if someone steps off the road in the dark), and the wizard has cast some sort of alarm spell on the road leading up to the encampment. The wizard also has Absorb Elements and Featherfall prepared.
If the party claims to be moving silently but talks or exchanges information in or out of character, the sentries and dogs hear them. Don't let them plan and claim to be silent.
The remaining bandits are in three groups with 5 bandits, and 2 dogs in each group, each group about 40' apart with one near the cook wagon. The last bandit is in the wagon with 100% cover. The dogs are alert and can effectively see in the dark and make perception checks to smell or hear approaching PC's as well. Barking dogs will investigate disturbances after one round.
In combat, the bandits disperse and take cover amongst the surrounding trees or behind the wagon. They only go to melee if the PC's are close. Sentries not directly engaged will make their way to the combat as stealthily as possible, trying to attack the party from flanks or rear.
What makes combat challenging is fog of war. Even more so than numbers, limiting the PC's information is what makes things difficult for them. If they have perfect information they'll easily make a perfect plan.