Nilshai

Nilshais were strange and evil sorcerous aberrations native to the Ethereal Plane. They were occasionally called ethereal theurges by star elves.

Description
Nilshais had worm-like bodies with three clawed legs and three slender tentacles for arms that each ended in three stubby but strong fingers. It had a bulbous head that sat atop its worm-like body with three eye stalks that each ended in a large eye. It also had three membranous wings that tightly folded along its trunk when not required. A nilshai had a soft, slimy, and slick hide that was mottled blue and black, but their flesh underneath was extremely hard.

Combat
When it felt threatened, a nilshai profligately hurled spells at a foe in order to kill them as quickly as possible. When faced with spellcasters, a common tactic of the nilshai was to cast a spell and then immediately cast a counterspell to dispel any magic that might be forthcoming from its foe. Their hard bodies were difficult to damage without magical weapons.

Abilities
They could quickly and easily shift back and forth between the Ethereal and Material Planes as they willed, similar to an ethereal jaunt spell.

Because of their trilateral symmetry and alien minds, nilshais were adept at multitasking. Able to do more at a time than others, they could attack or use their magic, and then use magic again immediately afterward. It also meant they had keen senses and were skilled at using unfamiliar magical items.

They were also naturally resistant to spells and other supernatural effects that could detect them or affect their alien minds, in a way similar to mind blank.

Nilshairs were natural sorcerers and quite powerful in arcane spellcasting.

Activities
These malevolent alien beings usually dwelled on the Ethereal Plane, yet occasionally entered the Material Plane on expeditions to seize lore and magic.

When on the Material Plane, a nilshai was almost always pursuing a purpose, whether searching for magical items, engaging in espionage, or looking for slaves (intelligent humanoids) to abduct to its home plane. It accepted no interference in its activities from residents of the Material Plane.

In particular, they had invaded Sildëyuir, the extraplanar home of the star elves, for several centuries. Despite it not being coterminous, they bored several portals through the dimensions to access the demiplane. These altered the plane's essence, and by 1370 DR they threatened to destroy the plane while the nilshais had begun to assault the stars elves' citadels.

Society
Very few in the Material Plane or Sildëyuir knew anything about nilshai society or their activities.

Nilshais were encountered either operating alone or in infestations of up to four together with three to six ethereal marauders.

The cities of the nilshais on the Ethereal Plane were strongholds built of ethereal stone, bizarre in shape and with complex chambers and twisting passages that were enough to drive a trespasser mad. Large strongholds could have about five-hundred nilshai residents, but most nilshais lived in communities of about fifty. A stronghold was led by its most powerful sorcerer, who ruled with absolute authority and assumed full obedience from all the others.

Within their strongholds, nilshais kept ethereal marauders as pets and ethereal filchers as servants. They also had ethereal slayers. Nilshais sometimes used other, weirder, creatures as guards and raiders.

Nilshais worshiped the Far Realm entity Mak Thuum Ngatha, the Nine-Tongued Worm.

Appearances

 * Adventures:
 * The Twilight Tomb