A notion I was kicking around that I wanted to pitch and see what people can do with it.
While aboleth traditionally do not follow any deity, given that (unless I am mistaken) they are considered 'young upstarts' unworthy of attention, lets imagine for a moment a group of Aboleth that have taken to following ZK in some sense.
How might they interpret and follow the tenants different than we do?
How would they approach inflicting upon themselves and others pain? You or I could pick up a whip, a knife, some chains, ect.. but these aren't exactly practical options for them.
What could drive a group of aboleth to serving/revering/respecting/ect. Zon-Kuthon in the first place?
How could/should such a group be statistically represented any differently from standard aboleth, if there would be such a difference in the first place? For instance; a group that dwells on another plane might have a template or two. A group drawn in perhaps forcefully at first might be victim to the Shadow corruption.
You could give them the Apostle Kyton template, to signify their devotion to ol' ZK. While that template is typically only for humanoids, I think it could work for anything with an unusual connection to Zon-Kuthon or the Shadow Plane in general. As for the roleplaying aspect, well you should consider that these aboleth would be seen as extremely heretical by, well most every aboleth that they ever met. The WHY they are Kuthoninites in the first place is the most important question to answer. Perhaps the aboleths in question were part of an aboleth exploration of the Dark Tapestry, maybe even getting spaced, and came to the conclusion that the dark and the void is the natural form of existence, and seek to return the world to that. Other options include being captured and tortured by an a mad archmage and turning ZK worship as a way to deal with the pain, somehow having kyton ancestry, thus skewing their minds into a most un-aboleth like state, or maybe they encountered a group of Kuthonites or kytons who have magically compelled them in to working for ZK. The possibilities are endless, just pick out one that works best for your group and setting.
Hope my rambling helped in some way.
You could give them the Apostle Kyton template, to signify their devotion to ol' ZK. While that template is typically only for humanoids, I think it could work for anything with an unusual connection to Zon-Kuthon or the Shadow Plane in general. As for the roleplaying aspect, well you should consider that these aboleth would be seen as extremely heretical by, well most every aboleth that they ever met. The WHY they are Kuthoninites in the first place is the most important question to answer. Perhaps the aboleths in question were part of an aboleth exploration of the Dark Tapestry, maybe even getting spaced, and came to the conclusion that the dark and the void is the natural form of existence, and seek to return the world to that. Other options include being captured and tortured by an a mad archmage and turning ZK worship as a way to deal with the pain, somehow having kyton ancestry, thus skewing their minds into a most un-aboleth like state, or maybe they encountered a group of Kuthonites or kytons who have magically compelled them in to working for ZK. The possibilities are endless, just pick out one that works best for your group and setting.
Hope my rambling helped in some way.
From the statistical side of things; Thats a good idea. I considered the dark template or shadow corruption template, but that certainly is more flavorful.
Apostle Kyton (Aboleth) CR 9
XP 6,400
LE Huge outsider (aquatic, augmented aberration, kyton, native)
Init +7; Senses darkvision 60ft.; Perception +17
Aura mucus cloud (5 feet; DC 23)
DEFENSE
AC 24, touch 9, flat-footed 23; (+1 Dex, +15 natural, –2 size)
hp 84 (8d8+48); regeneration 4 (good weapons, good spells, silver weapons)
Fort +11, Ref +7, Will +14
Immunity cold; SR 20
OFFENSE
Speed 10 ft., swim 60 ft.
Melee 4 tentacles +10 (1d6+5 plus 1 bleed plus slime)
Space 15 ft.; Reach 15 ft.
Special Attacks agonizing prayer (8d6, DC 24), bleeding touch (1), seductive oration (2d6 Wisdom or 4 sanity, DC 20), slime (DC 23), unnerving gaze (30ft.; DC 20)
Spell-Like Abilities (CL 16th)
At will—hypnotic pattern (DC 18), illusory wall (DC 20), mirage arcana (DC 21), persistent image (DC 21), programmed image (DC 22), project image (DC 23), veil (DC 22)
3/day—dominate monster (DC 25)
STATISTICS
Str 26, Dex 16, Con 28, Int 17, Wis 23, Cha 23
Base Atk +6; CMB +13; CMD 24 (can't be tripped)
Feats Improved Initiative, Iron Will, Lightning Reflexes, Weapon Focus (tentacle)
Skills Bluff +18, Heal +18, Intimidate +21, Knowledge (any one) +14, Perception +17, Spellcraft +14, Swim +27; Racial Modifiers +4 Bluff, +4 Heal, +4 Intimidate, and +8 Swim
Languages Aboleth, Aklo, Aquan, Infernal, Undercommon
SQ shadow traveler
And thats just the standard aboleth. Veiled Masters could be pleasant, not to mention omnipaths and any creature that is created and serves such aboleth.
Your rambling does help. There are many ways they could wind up there. A group of ambitious kyton could have even come and inflicted their brand of enlightenment upon a group of aboleth, and others of their kind have been inducted with time. Perhaps, given the role they have to play, one of the first convert was an Omnipath.
You could also play up these rogue Aboleths as not so much worshipping Zon-Kuthon as having entered an arrangement with him. Perhaps they have a long-term goal that they share with ol' Kuthie, and said God has granted them power to aid in their pursuit of said goal.
Even in this case, they'd probably be seen as very odd by other Aboleths at the very least.