Gravislayer
Large Aberration
Hit Dice: 8d8+11 (47 hp)
Initiative: +2 (+2 Dex)
Speed: 10 ft., fly 60 ft. (good)
AC: 20 (–1 size, +2 Dex, +9 natural)
Attacks: Bite +9
Damage: Bite 2d6+4
Face/Reach: 5 ft. by 5 ft. /5 ft.
Special Attacks: Gravity nexus
Special Qualities: Blindsight, gravity null
Saves: Fort +5, Ref +4, Will +4
Abilities: Str 18, Dex 14, Con 17, Int 4, Wis 7, Cha 13
Skills: Disguise +2, Hide +8, Listen +3, Search +1, Spot +6
Feats: Dodge, Toughness
Climate/Terrain: Any space
Organization: Solitary
Challenge Rating: 8
Treasure: Standard, Double Gems
Alignment: Always neutral evil
Advancement: 9–16 HD (Large); 17–24 HD (Huge)

    The gravislayer is a navigational hazard hated by spelljammers throughout the Known Sphere. Its body is a six feet diameter sphere of flesh that has been pitted and scarred from the rigors wildspace. They have no eyes, ears, or other features readily visible other than its maw.

Combat
    The gravislayer's preferred weapon is its gravity nexus supernatural ability to crush the flesh and bone of its opponent, which it will feed upon after the creature has breathed its last breath. As a last resort it will use its bite attack.
    Blindsight (Ex): A gravislayer can ascertain all foes within 100 feet as a sighted creature would by using its ability to see gravity, even that generated by medium sized and smaller creatures.
    Gravity Nexus (Su): The gravislayer may cause a targeted object, creature or location to be gravity nexus, causing all unattached objects and creatures within it to 'fall' toward the gravity nexus and reaching the nexus before the end of the round. Those who are within 100 feet of the gravity nexus are allowed to make a Reflex save to secure themselves when the spell strikes, provided there's something for them to hold onto. Creatures who can fly or levitate can keep themselves from 'falling'. Those who fall towards the nexus will strike it and take damage as they would during a normal downward fall, creatures at the outer edge of the area effect will take more damage then those close to the nexus (unless another object comes crashing on them). The following chart shows the damage a character takes from objects in the surrounding he is in.

Gravity Nexus Damage Table
  Deep     Asteroid Field &
Creature Target/In Area Space* Orbit* Ring Planet Bound
Gravity Nexus Target 17d6 18d6 20d6 25d6
Falling Targets 2d6 + falling 3d6 + falling 5d6 + falling 10d6 + falling
Targets not Falling 2d6 3d6 5d6 10d6
* DM should judge if sufficient number of objects exist that could cause this amount of damage.

    When the gravislayer cease concentration or when it is slain, creatures will align with any other natural gravity in the area, possibly resulting in more falling damage. If creature was the target of the gravity nexus and the its effects end he or she then can make a strength check at DC 18 to break free of debris.
    If DM needs to adjudicate individual damage by falling objects, then use the following as a guideline: Objects from 1 to 10 pounds cause 1d6 damage, objects from 11 to 50 pounds cause 2d6 damage, objects from 51 to 100 pounds cause 3d6 damage, objects from 101 to 200 pounds cause 5d6, and finally and object 200 pounds or more in weight causes 10d6 damage.
    Gravity Null (Ex): The gravislayer is not subject to any natural gravity less then that of planetary level, this includes the effects of Gravity Nexus.

In the Spheres
    Gravislayers have no known planet of origin or societal inclinations. Shipboard tales speak of a cult of nebulords, wizards of tremendous power, who were enemies of the reigar and the creators of the gravislayers. It is said that the nebulords set loose the gravislayers into the spheres to hunt down and crush the reigar.


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Gravislayer, © 1990 Wizards of the Coast, Inc.
d20™ System, Conversion of Gravislayer ©2002, Flits3 and Mark Doolan
Original Source: Monstrous Compendium #7