Pastlives
1) As for the chaos brigade, I can’t give you any advice, because there are many sources, but not all of them are correct. I can only boldly list a few: the Old Faction of Satan, the Outcasts of the 5 Clans of Kyoto (mostly those who were half-bloods of another race or had a Holy Gear), the Hero Faction - a faction of people whose lives were destroyed by their own “Sacred Gears”; Nilrem - a faction of mages expelled from the Magic Council, led by Euclid Lucifuge; 2) Hydra - has: good protection and strength; fast regeneration; poisonous breath (depending on the species); duplication of limbs (factor as in legends, if you cut off one head there will be two in its place) 3) Ingvild Leviathan is a sensitive issue, but in most of the sources I read, she was in the Sitri hospital... Until the moment she was secretly sold to the old faction of Satan, and she was sold by the old men from the council. 4) Longinus is much easier to explain - from -due to the death of God (Yahwah in most sources), the system was in a semi-autonomous mode. Because of this, new invisible holy mechanisms began to appear, some of which could defeat the 13 of those created by Yhwach. And the Ingvild Leviathan mechanism is considered a candidate for Longinus, due to its power over the waters and dragons (and influence on the dragon gods)
Bueno, si quieres entender como los sacred Gear se convierten en longinus de forma natural, en otro fanfic hizo una referencia a que los portadores anteriores guardaron su esencia como si fuera un caché y su exceso más el poder del nuevo portador rompieron un limitante que los convirtió en un longinus. Como referencia te puedo dirigir a Gasper ya que su Gear estaba listo para evolucionar y su poder natural a la hora de nacer lo hizo crecer a longinus, se convirtió en un longinus al no poder soportar más poder, gasper despertó su poder completo más adelante lo que esencialmente significa que la gran acumulación de poder de los antiguos portadores lo volvió un longinus, pero si el portador no rompe el limite con su propio poder no revelara su fuerza como un longinus por si solo y quedara como un sacred gear regular.