The least dangerous of the new kobolds in SLASH'EM, swamp kobolds present little more danger than an ordinary kobold lord. They have only one higher HD, the same AC, and their weapon attack is very similar - in fact, the swamp kobold's 1d8 damage is slightly lower, on average, than the kobold lord's 2d4.
Kobolds are creatures that appear in many fantasy-themed works and media, which often borrow significantly from Germanic folklore - Germanic kobolds are a form of sprite that are generally benevolent if treated with kindness, but will respond to disrespect with anything ranging from pranks to even outright attacking and killing offenders.
Dungeons & Dragons in particular - and by extension, NetHack and many of its variants - depicts the kobold as a race of small reptilian humanoids with long tails, distantly related to dragons; earlier editions gave kobolds more dog-like features, which lead to many depictions of kobolds in Japanese media leaning harder in that direction after the popularity of the anime franchise Record of Lodoss War. Fantasy kobolds are often considered weak "cannon fodder" monsters that can be cunning and strong in groups, similar to goblins.
The race of kobolds are reputed to be an artificial creation
of a master wizard (demi-god?). They are about 3' tall with
a vaguely dog-like face. They bear a violent dislike of the
Elven race, and will go out of their way to cause trouble
for Elves at any time.