Once your fortress has accumulated a certain amount of wealth, kobold thieves will raid you in fortress mode, generally, but not always, timing their attacks to coincide with the arrival of caravans. Kobold thieves can even show up in winter. They are able to bypass any and all traps, and are an excellent reason to channel all traffic in and out of your fortress through a single location which should be guarded at all times. Once discovered and caught, a kobold can generally be killed by any armed dwarf and most unarmed civilians. Be warned though that even the lowliest kobold thief will carry a copper dagger, which can lead into severe injuries if you order an unarmed recruit to attack it.
Kobold raiding parties may occasionally show up to ambush your dwarves outside once kobold thieves have successfully stolen some items. The kobolds will hold back and fire their bows at all dwarves who venture near. This is not a siege. The kobolds will leave when they have no more arrows or when they experience minor casualties. Due to the archers, these raiding parties can be quite dangerous to an unprepared fortress, especially one reliant on resources such as trees and surface water. The parties can also consist of other kobolds, such as kobold spearmen.
 Kobold Caves in Fortress Mode
Occasionally, on maps that have caves present in them, you'll find a kobold cave. These pose a possible hazard to your dwarven settlers, as -- should they discover you and become irritated at your presence -- they will attack your settlement and any wandering dwarves they come across. As mentioned previously, kobolds aren't very tough, but when they gather in large numbers (with more than a few armed kobold guards and other nasty variations of the common kobold thrown in) they can pose a significant threat to your young, underprepared fortress. On the upside, in the vicinity of the kobold cave and inside the cave itself, you'll find all kinds of random trinkets and other items, with the possibility of valuable goodies being tossed in. If you manage to clear the kobold cave on your map, any potentially valuable junk that they've accumulated is yours for the taking.
 Living Among Them
It is also possible to settle on a kobold cave that is not hostile to your fortress. This is most-likely unintentional, but could prove to be permanent depending on how kobold diplomacy is handled in the future. In the 'u'nits menu, the kobold inhabitants will be listed as "Friendly". Settling on a friendly kobold cave will be roughly equivalent to settling next to (or on top of) a human town, the main differences being that there will be no food stores or wooden furniture and no wooden housing to commandeer. The caves are useful, like any other cave, in exposing minerals, gems, rocks and ore veins from the outset of your fortress. This is the most common type of kobold cave you are likely to find.
Friendly kobold caves boast an assortment of animal and plant specialists, guards and the occasional weapon-master and will work with the dwarves in repelling sieges, kobold and goblin thieves, and ambushes. They will not be hostile to dwarven traders, but may attack traders from a civilization they are at war withVerify. Friendly kobolds will meander little, often staying in the same spot for years and they will not set off traps unless rendered unconscious by wounds on top of them, nor be targeted or hurt by catapult fire. Kobolds in fortress mode do not sleep or eat currently, and their created wealth is added to your own at embarkation.
It is also possible to find named hostile animals and other beasts living in the same cave as the kobolds. These will attack any kobold or dwarf that comes in contact with them.
 Kobold Caves in Adventure Mode
In adventure mode kobolds live in caves. They will have guards, soldiers, civilians, children, and the occasional quite dangerous weaponmaster. Kobolds are deadly with a bow but generally an easy match in melee, even for a novice adventurer. Kobold caves are full of trinkets, and they often wear clothing, weapons, and small-sized armor.
[CREATURE:KOBOLD] [NAME:kobold:kobolds:kobold] [TILE:'k'][COLOR:6:0:0] [GLOWTILE:'"'][GLOWCOLOR:6:0:1] [LOCKPICKER][TRAPAVOID][FLEEQUICK] [GENPOWER:2] [CAN_CIV][CAN_LEARN][LIKES_FIGHTING] [BONECARN] [CANOPENDOORS] [PREFSTRING:mischief] [BODY:HUMANOID:2EYES:2EARS:NOSE:2LUNGS:HEART:GUTS:ORGANS:HUMANOID_JOINTS:THROAT:NECK:SPINE:BRAIN:5FINGERS:3TOES:MOUTH] [SIZE:5] [MAXAGE:150:170] [ATTACK:MAIN:BYTYPE:GRASP:punch:punches:1:2:BLUDGEON][ATTACKFLAG_WITH] [ATTACK:SECOND:BYTYPE:MOUTH:bite:bites:1:2:GORE][ATTACKFLAG_CANLATCH] [CHILD:12][BABY:1] [FAT:1] [EQUIPS] [NOCTURNAL] [UTTERANCES] [STANDARD_FLESH] [HOMEOTHERM:10067] [SWIMS_LEARNED][SWIM_SPEED:2500] [PERSONALITY:ANXIETY:50:75:100] [PERSONALITY:TRUST:0:25:50] [PERSONALITY:ACTIVITY_LEVEL:50:75:100]