[The arkamoi was the second weakest of the ushemoi originally, at a CR 4. The star spawn seer, on the other hand, is the second strongest of the 5e star spawn, at a CR 13. Something something assumption that spellcasting is stronger than martial abilities. My mechanics hew pretty close to the 5e version, but I gave it the foul insights of the 4e version. I wanted to justify calling it a seer, you know?]
Foulspawn Seer
CR 12 CE Aberration
This creature is swollen and misshapen, as if it were a tumor sculpted into a humanoid form. Its face is piggish, with an upturned nose and beady eyes. Its skin texture is filled with whorls and loops of tissue, like the surface of a brain, although tentacles and antennae grow from it at irregular intervals. It carries a staff made of bone and sinew in its clawed, webbed hands.
Foulspawn seers are more powerful and vastly more intelligent than most other foulspawn. They are the masterminds of the ushemoi, maintaining spawning pits on Aucturn and leading missions of madness and destruction on other planets. They can teleport between worlds, and given a few days, a handful of foulspawn seers can deliver an entire army of foulspawn to a new location. The tentacles that grow from their body are sensory organs that can feel vibrations, pick up scents, and detect subtler stimuli. Foulspawn seers are called arkamoi in Aklo.
A foulspawn seer uses its mastery of cosmic forces in combat. Their comet staffs are charged with the force of high gravity and phenomenal velocity, and can deal force damage at both melee range and at a distance. They can teleport at will, and often use this ability to trade places with their minions in order to let them absorb blowsâa wise fighter of foulspawn will kill the rest of the envoy before dealing with the seer, or otherwise curtail their ability to teleport. A foulspawn seer can even use teleportation offensively, creating a miniature wormhole that transports and crushes foes simultaneously. Other foulspawn fight better with a seer in their ranks, its mad insights feeding into their minds telepathically.
Foulspawn Seer         CR 12
XP 19,200
CE Medium aberration (foulspawn)
Init +2; Senses blindsight 30 ft., darkvision 60 ft., Perception +18
Aura foul insight (20 ft.)
Defense
AC 27, touch 18, flat-footed 25 (+2 Dex, +6 insight, +9 natural)
hp 152 (16d8+80)
Fort +12, Ref +9, Will +15
DR 15/magic; Immune confusion and insanity effects, mind influencing effects; Resist cold 10
Defensive Abilities bend space, insightful defense
Offense
Speed 30 ft., out of phase movement
Melee comet staff +17/+12/+7 (1d8+7 plus 2d6 force) or 2 claws +16 (1d6+4)
Ranged 2 warp orbs +14 touch (5d6 force plus stun)
Special Attacks collapse distance
Spell-like Abilities CL 16th, concentration +21 (+25 casting defensively)
At willâdimension door, dimensional anchor, mind thrust III (DC 18)
3/dayâconfusion (DC 19), quickened dimension door, shield, telekinesis (DC 20)
1/dayâego whip IV (DC 21), interplanetary teleport, psychic crush II (DC 21)
Statistics
Str 18, Dex 15, Con 21, Int 22, Wis 8, Cha 21
Base Atk +12; CMB +16; CMD 28
Feats Combat Casting, Dimensional Agility, Great Fortitude, Iron Will, Lightning Reflexes, Point Blank Shot, Precise Shot, Quicken SLA (dimension door)
Skills Bluff +21, Intimidate +24, Knowledge (arcana) +25, Knowledge (dungeoneering, geography, religion) +22, Perception +18, Sense Motive +18, Spellcraft +25, Stealth +21
Languages Aklo, Common, Draconic, Elder Thing, Undercommon, telepathy 60 ft.
SQ madness, no breath
Ecology
Environment any land or underground
Organization solitary, cult (2-3) or envoy (1-3 plus 1-8 mixed foulspawn)
Treasure incidental (masterwork morningstar, other treasure)
Special Abilities
Bend Space (Su) As an immediate action when it would be hit by an attack, a foulspawn seer may teleport to the space of another foulspawn within 60 feet, and teleport the foulspawn to its space. This results in the attack hitting the other foulspawn and the seer taking no damage. A foulspawn seer can use this ability a number of times a day equal to its Intelligence modifier. This is a teleportation effect.
Collapse Distance (Su) As a standard action, a foulspawn seer can teleport another creature of its choice within 60 feet. If the creature succeeds a DC 23 Will save, it does not teleport, but takes 5d6 points of force damage. If it fails, it takes 10d6 points of force damage and teleports to another square of the foulspawnâs choice within 60 feet of its original position. All creatures within 10 feet of its original position take 5d6 points of force damage (Fort DC 23 negates). This is a teleportation effect. A foulspawn seer can use this ability 3 times a day, but must wait 1d4 rounds between uses.
Comet Staff (Su) By spending eight hours, a foulspawn seer can transform a staff into a comet staff. This functions as a +1 morningstar. In the hands of the foulspawn seer, it deals an additional 2d6 points of force damage on a successful hit, and is required as a focus to use its warp orbs. These abilities function for no other creature, including other foulspawn seers. A foulspawn seer can only have a single comet staff at a time.
Foul Insight Aura (Su) All foulspawn within 20 feet of a foulspawn seer may choose to roll twice on a single attack roll, saving throw or skill check each round and take the better result. The foulspawn must declare that it is using the ability before knowing the result of the roll.
Insightful Defense (Ex) A foulspawn seer gains an insight bonus to its Armor Class equal to its Intelligence modifier. It only loses this ability if helpless or stunned.
Madness (Ex) Foulspawn use their Charisma modifier on Will saves instead of their Wisdom modifier, and are immune to insanity and confusion effects. Only a miracle or wish can remove a foulspawn's madness. If this occurs, the foulspawn gains 6 points of Wisdom and loses 6 points of Charisma.
Out of Phase Movement (Su) A foulspawn seer can move through solid objects and squares occupied by enemy creatures. It provokes attacks of opportunity as normal for this movement. If it ends its movement inside a solid object, it is shunted to the nearest empty space and takes 1d10 damage. A foulspawn seer under the effects of a dimensional anchor or similar effect cannot use this ability.
Warp Orb (Su) A foulspawn seer can fling a single warp orb from its comet staff as a standard action, or two as a full round action. Treat these as ranged touch attacks with a range of 80 feet and no range increment. A creature struck takes 5d6 points of force damage and must succeed a DC 23 Will save or be stunned for 1 round. The save DC is Charisma based. A warp orb is blocked by a shield spell or brooch of shielding as if it was a magic missile spell.