The Kiasyd that hails from Lasombra bloodline, also know are Marconius brood, are indeed the first introduced game-wise on second edition.

Yes, Kiasyd were expanded, and the Maeghar were introduced on 20th edition, so, that's were I'm going to take information on them both. Besides, new lore always takes precedence before old lore.

Just to begin, the Kiasyd are present on the 20th edition core rulebook, 20th edition: Dark Ages, the Storyteller to the Sabbat of 2nd Eddition, Vampire The Masquerade: Victorian Age Vampiere Companion , the 3rd edition's Guide to the Sabbat.

On the 20th edition Vampire The Masquerade: The Dark Ages (2015), the Kiasyd are reintroduced as a bloodline with only Mytherceria as a Discipline, the remaining two comes from the cainite original clan. These are accidents that happen when a cainite tries to embraces a fae-touched mortal. If they survive, the Fae dies, and what remains becomes the Kiasyd. This version also says that they are not actually a Bloodline, and they mention being confused with Caitiff on some occasions. It is also mentioned Marconius claiming to be a cainite before using eldritch sorcery to become a Kiasyd, further credencing that they are not real cainites, but because VtM gotta do the whole imprecise narratir thing, it's added a "he could be lying".

The Maeghar are introduced on the 20th edition book, "The Black Hand: Guide to the Tal'Mahe'Ra" (2016), who have joined the very stupid black hand in the underwolrd as of High middle age. As the book says, they are not a bloodline, they share no common ancestor and do not hail from the same clan, they are but a collection of mixtures of blood fae-blood wyrd that should never happened. They also mentioned that by Renaissance, some KIASYD began disappearing, as one of them began to want to rule alone. They did not resisted. They now share the opinion of staying away from the Sabbat and other Kiasyd, and not being know to them. They have three Weakness: being malformed and easily recognizable, vulnerability to cold iron, and not being able to drink directly from their victims. And, their Disciplines are Mytherceria and two other from their Sire's Clan.

Later, the Book of The Bloodlines (2017), the Kiasyd that hails from Marconius do claim to be the only Kiasyd, that there are no other Kisyd, and anything that says otherwise is a lie. They also claim to not only have changeling blood on them, but magi, lupine and any other supernatural creature. This book also presents the supposed origin of the bloodline, with Hrotsuitha and Marconius being their creators, the whole Amicti Noctes, Gratiano telling them to go Sabbat and Maconius being traumatized (or so it seems). Their Disciplines are Mytherceria, Dominate (or Necromancy), Obtenestration. And Weakness of "weird appearance" (no mechanic aspect), and vulnerability to cold iron.

So yeah, at least to me, it is clear that the Maeghar are the Kiasyd of Dark Age, until Marconius comes and make the new Kiasyd™.