Promethean
A variant of Zoanthids (Zoanthus sp.)

Photo: Kazvorpal · CC BY-SA 3.0
Representative Zoanthids image. A confirmed image of this exact morph isn't available yet.
Among the darkest zoas, it can look black when lit by blue LEDs. Its dark colour is the whole appeal.
Other Zoanthids variants
Eagle EyeRastaBrown/wild button polypsBlue HornetRainbow IncineratorPeople EaterUtter ChaosFruit LoopsSunny DWWC BowsersArmageddonGorilla NippleDaisy CutterTubbs BlueMagicianGobstopperBlow PopPink ZipperKrakatoaSpeckled KrakatoaGrand Master Krakatoa (GMK)Whammin WatermelonBam BamDaisy DukeKing MidasMy ClementineGoblins on FirePink DiamondsLunar EclipseNuclear GreenArmor of GodBob MarleyPandoraWildflowerRainbow HornetJF BloodshotEye of RaGreat Owl ZoaPunk RockerPurple HornetBlueberry FieldsStratosphereQueen StratSupermanKryptonitePlayboy BunnyDarth MaulSakuraGreen Bay PackersBlue AgaveChucky's BrideGod of WarBlack Hole SunBlue SteelCat's EyeCreamsicleEye of SauronIncredible HulkFrozen ArmageddonNebulaAngel WingsStarscreamSun EaterJungle JuiceMandarinSolar FlareKung Fu FighterDeath StarNirvanaMean GreenScrambled EggsRed HornetStrawberry WineMiami ViceMary JaneTaserPink KrakatoaBlue Eyed BlondesAOICandy Apple RedAlien AntivenomGatoradeOompa LoompaSweet ToothOrange OxideSonic FlareSpace ChaosWhite ZombieBloodsuckerKedd's RedsMohawkCandy CrushFairy MuncherUltimate FireToxic RainTequila SunrisePurple HeartOrange Dragon EyeMambo JamboPumpkin SeedsLittle Shop of HorrorsYellow SubmarineFrozen NebulaCharmanderBlue Boo BerryVampireSour PunchPacmanFake ChiliNightmareRasta CousinsOrange RainbowSpellbinderGod BeastPredatorFrozen HornetTiger HornetJawbreaker HornetMurder HornetAcid RainSuperstarZombie EyeInsane RainbowPunch DrunkSafecrackerMystiqueBansheeTwizzlersAphroditeLaffy TaffyEmeralds on FireAtmosphereAntimatterLA LakersTutti FruttiAwesome BlossomBlack BellaExosphereSnowglobeSuper SaiyanGold MaulHalle BerryKoala EyesFruitopiaPerennial DanceOmegaRing of Fire