Glottkin
The Glottkin are triplet-brothers and champions of Nurgle, who are the titular stars of the second volume of books released for The End Times.
Story
Despite their allegiance to Nurgle, the Glottkin are actually Imperial by blood; the sons of a Nordlander father, Ollos Glotts, and his wife, a Life mage named Ethra Greenblood. The Glotts came to Norsica on a secret mission; by living peacefully alongside the Norscans of the fjords of the Sea of Claws, showing them the healing arts of the Wind of Life and more advanced methods for coaxing successful crops, they hoped to slowly break the chains of hatred that compelled the incessant cycle of raids and retaliations.
For some time, the two were welcome, becoming quite influential, but a jealous Norscan hag cut Ethra's finger with a cursed rusty knife during her pregnancy with her sons. Unable to break the hag's curse herself, Ethra pleaded with the gods to spare her children, and Nurgle took pity, curing the infection and allowing for the birth of three healthy boys; Otto, Ethrac and Ghurek. Each was healthy and hearty, the only sign of their future fate a birthmark with three lobes that each bore on their body.
Their efforts were doomed when a Nordlander force came to Fjordlingtribe land in 2506; the Glotts took up arms to defend their friends and neighbors, and the brothers saw their parents murdered by the Imperials. From that moment on, their souls belonged to Nurgle.
Ghurek devolved into a monstrous beast, an eating machine capable of swallowing men whole and then shitting them out as grotesque Chaos Spawn, to the point his own brothers took to calling him Ghurk and using him as a steed. Ethrac became a powerful sorcerer of Nurgle, using the black arts to slay and murder. And Otto turned his former scythe into a lethal killing tool as a champion of Nurgle.
They were chosen by Archaon to lead his second invasion during the End Times, allied to the Maggoth Riders and to Gutrot Spume. At the verge of victory, though, they were defeated, changing into fly swarms to escape death at the hands of a divinely empowered Karl Franz. Now the triplets are trapped in jars in Nurgle's attic, for Nurgle is very displeased with them...
Rules
On the tabletop, the Glottkin fight as a single Special Character Monster, since Otto and Ethrac always ride little brother Ghurk into the fray. They cost 810 points and use up a Lords slot. They have Movement 6, Weapon Skill 6, Ballistic Skill 3, Strength 6, Toughness 6, an insane 12 Wounds, Initiative 1, 5 Attacks and Leadership 10. They have the Nurgle's Rot mutation, and the common special rules Eye of the Gods, Impact Hits (D3), Mark of Nurgle, Poisoned Attacks, Regeneration and Terror. They also have the unique special rules of Ethrac Glott (they're a level 4 wizard using the Lore of Nurgle), Ghurk Glott (chose one attack per round; this one is S10 and Multiple Wounds (D6)), Otto Glott (gain +D6 attacks at the start of each Close Combat Phase), Lords of Nurgle (Glottkin and Nurgle-marked units within 12" re-roll failed charges, Glottkin always get the Aura of Chaos reward when rolling on the Eye of the Gods), and Pestilential Torrent (Strength 3 Breath Weapon that ignores armor, can only be used in close combat).
While this all sounds impressive, the issue with the Glottkin is that unlike the other behemoth model (Nagash), they get no real bonuses to boost themselves or their forces, for example Nagash has triple the range and summon costs from the Lore of Undeath, but the Glottkin gain no such bonuses for the Lore of Nurgle or the new "Summon Infernal Legion" spell (it should be noted that the Summon Infernal Legion spell is specific to the "Chaos Ascendant" special scenario ruleset, and is not a universal new rule- you only get it if you are playing one of the special scenarios or your opponent otherwise agrees to it). Taking the trio means that they'll either need to be in constant combat in order to make back their points' worth, or you're going to be casting that summon spell as often as possible (if not both "Summon Undead Legion" and "Ryze - The Grave Call" to get two summon spells out of them), but again, unlike Nagash they have no protection at all against miscasts and at their cost means you don't want to take that risk unless you're badly losing the game. Lastly as a monster, they cannot join units and so can be picked out by mass archer spam or siege machines.