Nilshai

Nilshai are sorcerers native to the Ethereal Plane and are sometimes referred to as ethereal theurges by star elves.

These malevolent alien sorcerers spend most of their time on the Ethereal Plane, but they sometimes mount expeditions to the Material Plane to obtain lore and magic. They are servants of the Abolethic Sovereignty and have been invading Sildëyuir, the extraplanar home of the star elves, for several centuries, making portals to the demiplane that alter the plane’s essence, and have recently begun to assault the stars elves’ citadels.

When on the Material Plane, a nilshai is always on a mission, whether searching for magical items, engaging in espionage, or looking for slaves to take to its homeland. When residents of the Material Plane interfere, nilshai profligately hurl spells at them in order to kill them as quickly as possible. When faced with spellcasters, a common tactic of the nilshai is to cast a spell and then immediately cast a counterspell to dispel any magic that might be forthcoming from its foe. They can quickly shift back and forth between the Ethereal and Material Planes, and they are naturally resistant to spells and effects of detection and mental influence. Because of their trilateral symmetry and alien minds, nilshai are adept at multitasking.

Physical description
The nilshai have worm-like bodies and three clawed legs. They have three slender tentacles for arms that each end in three stubby fingers. A nilshai has a bulbous head that sits atop its worm-like body with three eye stalks that each end in a large yellow eye. It also has three fly-like wings that tightly fold against its torso when not in use. Nilshai have a soft, slimy, and slick hide that is a mottled blue and black, but their flesh underneath is extremely hard.

When slithering on the ground, nilshai move in a rolling corkscrew fashion, different limbs touching the ground at different times.

Society
Very few on the Material Plane or Sildëyuir know anything about nilshai society or organization. The cities of the nilshai are bizarre stone strongholds on the Ethereal Plane that have extremely complex, mazelike chambers and twisting passages. Large strongholds can have about five hundred nilshai residents, but most nilshai live in communities of about fifty. A stronghold’s most powerful sorcerer is its absolute ruler, commanding the obedience of all the others.

Nilshai keep ethereal marauders as pets and ethereal filchers as servants. Their strongholds also have ethereal slayers. Nilshai sometimes use other creatures as guards and raiders.

In the default setting of Dungeons & Dragons, nilshai worship the Far Realm entity Mak Thuum Ngatha, the Nine-Tongued Worm, as stated in Lords of Madness.