Abandoned Outpost

Arriving at a small clearing high on the hillside, you have found a building with attached stable and gated yard. Unfortunately, the gate has been knocked off, as has the front door of the main building. The northern wall of the building is dominated by a towering second story with slits opening in the middle of its upper wall. From the far side of the building there is smoke rising. It doesn't appear to be on fire, but the smoke is rising from the entire length of the building, indicating recent trouble.
The whole place seems deserted, though a large fight clearly took place. There are signs of horses running off down the trail, chased by much smaller feet (Survival DC12 will recognize them as kobold prints). A thorough search of the main building will show many bodies, kobold and men, and a few goblins as well. The back half of the building is badly burned, with gaping holes in the rear wall and roof. Looking through them shows the whole river valley laid out below the clearing, clearly an advantage of this location.
In a large room to the left of the entrance, there is a staircase spiraling up into the tower. The upper floor is scattered with discarded and broken weapons. There are arrow slits in each wall giving coverage to the surrounding area. In the next room on the first floor there is a stairway leading into the basement.
Investigation DC15 will reveal that there were several potions and scrolls in the room at the back of the house, mostly consumed in the fire. If the check is 18 or higher, you recognize that the fire was set  intentionally to destroy the contents of this room. Searching (Perception DC15) will show three potions that survived the fire among the many smashed flasks (2 potions of healing and a potion of speed). DC18 will let them find three scrolls that escaped destruction (Alarm, Fog Cloud, and Sleep).
The rest of the first floor is scattered with broken items of all sorts. It appears that a dozen guards were stationed at the garrison. There are two larger rooms, one with sparse furnishings, the other with scribbled notes and arcane ingredients. If players look for a specific weapon or component, roll a percentile dice and give them a 10% chance of finding it among the wreckage.
Downstairs in the basement, little has been disturbed. There is dust and cobwebs everywhere, but no light sources. There are a number of small rooms carved out of the earth.
Perception DC12 to find a secret trap door in one room. In the room is an unconscious guard. He can be healed, but remains unconscious until he has had a long rest. Searching the sub basement can reveal a buried chest (DC18) with a mysterious orb inside.
While searching the building, the sun sets, leaving you to set up camp in the burned out building for the night. It does offer good shelter and protection, but it is also the target of an attack in the night. The kobold gang that ransacked it returned to their master with news of the victory, only to be savagely bullied for failing to recover the orb they were sent to find. They are sent back and attack in the night. There are 8 kobolds, 4 goblins, and 2 winged kobolds. There are many ways to play out the encounter, depending on where the players make their camp, what kind of watch they set, etc.