Hit Dice: 11D8+33 (88 hp)
Initiative: +1 (Dex)
Speed: 30 ft, 10 ft flying (clumsy), 10 ft burrow, 30 ft swimming
AC: 20 (+1 Dex, -1 size, +10 natural)
Attacks: 1 tail, +10 melee; 4 claws, +8 melee; 1 bite, +8 melee
Damage: Tail 2d12+4; claws 1d6+4; bite 3d6+4
Special Attacks: Tail sweep
Special Qualities: Damage reduction 5/+1, scent, improved grab, blindsight
Saves: Fort +6, Ref +4, Will +8
Abilities: Str 19, Dex 12, Con 17, Int 12, Wis 12, Cha 14
Skills: Climb +14, Escape Artist +5, Hide +11, Jump +9, Search +6. Move Silently +12
Feats: Multiattack, Weapon Focus (tail), Combat Reflexes
Challenge Rating: 10
Alignment: Usually neutral
Advancement: 12-13 HD (Large)
Yitsan are roughly humanoid creatures with somewhat reptilian features. They stand ten feet tall, with eight-foot long tails, and are covered in fine, greyish-green scales. Their hands and feet have four digits, each with long, sharp claws, their tails are covered with razor-sharp projections, and their mouths have three rows of teeth. They smell of salt, and they have no eyes, or any real indication of where eyes would have been. Their other senses are extremely acute, and they scent like snakes do, with their tongues.
Yitsan are sometimes called "treasure bane" or "intruder within," for their eggs, which are laid in groups of up to four, are gold-colored disks the size and shape of featureless gold coins, and are frequently collected as part of a treasure hoard. The eggs hatch quickly, and the infant yitsan resemble inch-long lizards, which, providing they have a steady diet (at this age they eat insects, mice, wood, cloth, and similar items) grow to a length of a foot in just a few weeks. While young, the yitsan have a natural camouflage ability which allows them to remain hidden. Immature yitsan have no attacks.
After they reach the length of a foot, the young yitsan undergo a rapid and painful metabolic change, and reach full both full size and maturity in just two hours. It will try to find a private place while going through this change, because it is completely helpless during it. This growth spurt leaves the yitsan ravenous; its diet becomes strictly carnivorous, and it immediately will go hunting. After it eats, it will locate a place with numerous gold coins and lay its first clutch among them.
Combat is what the yitsan does best, and if hungry or provoked will attack furiously.
Tail Sweep (Ex): The yitsan usually begins combat with a tail sweep. This only requires a single attack roll, versus the best AC of everyone within the arc of its sweep. Victims of the sweep must make a Reflex save (DC is the yitsans attack roll) or fall. Yitsan generally try to trample and claw prone victims with all four sets of claws.
Improved Grab (Ex): The yitsan can grab in two different ways: with its tail, and with its jaws. The yitsan can choose to wrap its tail around an opponent. If it successfully hits, it causes no damage that round; however, on subsequent rounds, it causes 2d4+4 damage from the constriction, plus 1d6+4 damage from the spikes on its tail (those in metal armor do not take this damage), until the victim escapes. The yitsan can, and will, attack other people with its claws and bite while holding someone.
The yitsan can also bite someone, causing the listed damage the initial round and an additional 2d6 damage each subsequent round, until the victim escapes.
Blindsight (Ex): Yitsan are blind, but their other senses make up for this. They are capable of "seeing" within 50. Outside of this range, all targets are considered to be totally concealed. Spells and other effects that rely on sight are useless against them; those that affect other senses reduces their blindsight to the equivalent of the Blind-Fight feat. If both are negated, the yitsan is effectively blinded.
From the 2e Spelljammer Monstrous Compendium