XILL

Xill are bipedal, flame-red creatures, with short, powerful bodies and four arms, all of which can wield weapons simultaneously. If un-armed, they fight with four claws for 1-4 hit points of damage each.

The high Dexterity of the xill not only accounts for its low armor class (its natural AC is 4) but also gives the creature a hit probability bonus of +3 when attacking (+5 with missiles).

The xill has apparently only one aim in life — to produce young; the creatures are asexual and reproduce by producing eggs which must gain sustenance prior to hatching in the stomach of a living human or near-human. Thus they will try to snatch victims alive.

Xill have the innate power of etherealness. They may transfer from the Ethereal to the Prime Material Plane in one segment (6 seconds), but the reverse process takes two melee rounds. A xill will usually initiate an attack by emerging suddenly from the Ethereal Plane near to a chosen victim, achieving surprise 90% of the time. 

In attacking, it will use two of its arms in an attempt to grapple its victim, while using the other two (which might carry weapons) to subdue. The subduing attacks are resolved in the same way as attacks to subdue a dragon. Upon announcement of intent to strike to subdue, all hit points of damage scored by attacks on the victim (from the two subduing arms) are considered non-fatal battering/bruising damage. Each melee round the following fraction is calculated.

Total number of 'subdual' hit points scored ÷ Total number of hit points of the victim

The result is converted into a percentage, and that is the percentage chance of the victim being subdued in that round. Percentile dice are rolled to determine the result and if the score is less than or equal to the percentage derived, the victim is subdued.

The grappling attacks are normal; both grappling arms must score a hit for the grapple to be successful, otherwise it is assumed that the victim has been able to avoid being grappled. However if the victim has previously been subdued, the grappling attack will always succeed in the next melee round. 

If the xill succeeds in grappling a victim, it will then inject a paralysing fluid into his bloodstream through its claws, (normal saving throw applicable) in the next melee round. 

Victims grappled thus have one melee round to break free before the fluid is injected, and they may attempt to do so by 'saving against Strength' — a d20 is rolled, and if the result is lower than the victim's Strength, he has escaped from the clutches of the xill.

In summary, the xill attempts to grapple and paralyse the victim, or to subdue and grapple him. Once either of these results has been achieved, it will attempt to become Ethereal (and its power to do so will extend to its paralyzed/subdued victim and carry the victim to its lair on the Ethereal Plane to inject the eggs. 

During this two-melee-round transitory period when the xill and its victim are turning ethereal, the xill cannot move, it is vulnerable to magic (i.e. its magic resistance is reduced to zero) and can be hit by weapons at -3 hit probability. When the transition is complete, however, the creature can only be attacked ethereally and its normal magic resistance is restored.

If attacked in its lair on the Ethereal Plane, the first priority of the xill will be to save and protect its young and to remove any egg-bound prisoners to a safe place, only then attacking the invaders.

The xill eggs hatch after 1-4 days in the victim's stomach; for the next 2-8 days the larvae collectively inflict 11-20 hit points of damage on the victim per day as they mature, and they then emerge from the victim, killing him instantly, as 2-16 small xill which grow rapidly (1-4 hours) into full-sized creatures.

Protection from evil will always succeed, on either plane, in warding off a xill.