In the DMG, they are described as "lively and full of humor - often on the black side or practical jokes".
They are described as living in homes: "sometimes based upon earthen burrows, although 75% of the time it will be made in rocky hill formations" (MM), and that they "enjoy the open world of growing things almost as much as their mines and burrows" (DMG). In short, just as we would expect someone with the instincts of both Leprecauns and Dwarfs.
In the MM, they are rumored to have "magical abilities". This is revealed in the PH to be illusionist skill, up to seventh class level (casting 4th level spells). These innate illusionist powers are developed more fully in the description of the Deep Gnomes, the Svirfneblin.
Svirfneblin: 3' tall with pointy ears, home: far beneath the surface of the earth
powers (1x per day):
blindness
blur
change self
non-detection and silent movement (constant)
unlikely to be surprised (1 in 12)
immune to illusion
(20-40% magic resistance)
Wee Folk - The Illusionist Tricksters
The Wee Folk have been classified according to a number of different titles, including leprechauns, brownies, pixies, sprites, and bookas. They seem to have a number of traits in common, suggesting they form something of a family group.
Their similarities to the Gnomes are manifold, including the pointy ears. The MM suggests that Brownies and Leprechauns are the result of a Halfling/Pixie combination. It seems just as likely that Gnomes are the result of a Dwarf/Leprechaun combination.
Brownies: 1.5' tall with pointy ears, home: quiet, pastoral areas; "friendly but shy"
powers (1x per day):
invisibility in nature (at will)
ventriloquism
dancing lights
continual light
mirror image
confusion
dimension door
protection from evil
cannot be surprised
Leprechaun: 2' tall with pointy ears, home: fair, green lands with lush hills and dales; "mischievous nature"
powers (at will):
invisibility
polymorph non-living object
create illusion
ventriloquism
cannot be surprised
(80% magic resistance)
Pixie: 2.5' tall, with wings and pointy ears, home: most idyllic of woodlands, "highly mischievous"
powers (at will):
invisibility
polymorph self
create illusions (2x per day)
know alignment
cause confusion
dispel magic (1x per day)
dancing lights (1x per day)
ESP (1x per day)
Otto's Irresistible Dance (1x per day)
(25% magic resistance)
Also related:
Sprites: 2' tall, with wings and pointy ears; home: meadows and wooded glens, "shy and reclusive"
powers (at will):
invisibility
detect good/evil
move silently
Booka: 1' tall, with wings and pointy ears: home: attics, roofs, chimneys; "mischievous but hates evil"
powers (at will):
invisibility
(10% magic resistance)
