Xill (CR 6)

Medium Outsider (Extraplanar)
Alignment: Always lawful evil
Initiative: +7 (+3 Dex, +4 Improved Initiative); Senses: darkvision 60 ft., Listen +9, and Spot +9

AC: 20 (+3 Dex, +7 natural), touch 13, flat-footed 17
Hit Dice: 5d8+10 (32 hp)
Fort +6, Ref +7, Will +5
Speed: 40 ft.
Space: 5 ft./5 ft.
Base Attack +5; Grapple +7
Attack: Shortsword +7 melee or claw +7 melee or longbow +8 ranged
Full Attack: 2 shortswords +7 melee and 2 claws +5 melee (or 4 claws +5 melee); or 2 longbows +4 ranged
Damage: Short sword 1d6+2/19-20, (2) short sword 1d6+1/19-20, claw 1d4+2, (2) claw 1d4+1, or longbow 1d8/x3
Special Attacks/Actions: Improved grab, paralysis, implant
Abilities: Str 15, Dex 16, Con 15, Int 12, Wis 12, Cha 11
Special Qualities: SR 21, planewalk
Feats: Improved Initiative; Multidexterity; Multiweapon Fighting
Skills: Balance +13, Climb +10, Diplomacy +2, Escape Artist +11, Intimidate +8, Listen +9, Move Silently +11, Spot +9, Tumble +11, and Use Rope +3 (+5 with bindings)
Advancement: 6-8 HD (Medium-size); 9-15 HD (Large)
Climate/Terrain: Ethereal Plane
Organization: Solitary or gang (2-5)
Treasure/Possessions: Standard

Source: Monster Manual

Improved Grab (Ex): To use this ability, the xill must hit with one or more claw attacks, The grapple check has a +2 bonus for each claw that hits. If it gets a hold and maintains it the next round, it automatically bites the foe at that rime. The bite deals no damage but injects a paralyzing venom.

Paralysis (Ex): Those bitten by a xill must succeed at a Fortitude save (DC 14) or be paralyzed for 1d4 hours. Barbaric xills secrete enough venom to bite two opponents every 6 hours, while their civilized cousins can bite only once per day.

Planewalk (Su): These planar travelers like to slip between the folds of space to attack enemies as though from thin air. They can cross from the Ethereal Plane with a move action but take 2 rounds to cross back, during which time they are immobile. As a xill fades away, it becomes harder to hit: Opponents suffer a 20% miss chance on the first round and a 50% miss chance on the second.

Implant (Ex): Xills lay their eggs inside paralyzed creatures. The young emerge about 90 days later, literally devouring the host from inside. A remove disease spell rids a victim of the egg, as does a successful Heal check (DC 20) by someone with that skill. If the check fails, the healer can try again, but each attempt (successful or not) deals 1d4 points of damage to the patient.

Feats: A xill receives the Multiweapon Fighting feat as a bonus feat. With its Multidexterity and Multiweapon Fighting feats, it can attack with all its arms at no penalty as a racial ability

Extraplanar Subtype

A subtype applied to any creature when it is on a plane other than its native plane. A creature that travels the planes can gain or lose this subtype as it goes from plane to plane. This book assumes that encounters with creatures take place on the Material Plane, and every creature whose native plane is not the Material Plane has the extraplanar subtype (but would not have when on its home plane). An extraplanar creatures usually has a home plane mentioned in its description. These home planes are taken from the Great Wheel cosmology of the D&D game (see Chapter 5 of the Dungeon Master's Guide). If your campaign uses a different cosmology, you will need to assign different home planes to extraplanar creatures.

Creatures not labeled as extraplanar are natives of the Material Plane, and they gain the extraplanar subtype if they leave the Material Plane. No creature has the extraplanar subtype when it is on a transitive plane; the transitive planes in the D&D cosmology are the Astral Plane, the Ethereal Plane, and the Plane of Shadow.