The Angels of Destruction were ancient serpent-like beings which resided in Hell since the days when Pluto was king. After Satan rose, they seemingly allied themselves with him and the Order of the Fly. After hearing that Azzael had put the Right Hand of Doom onto his newborn son, the other nobles of Hell deployed these beings to destroy the castle of the traitorous demon.
They were still alive even after the death of Satan and the Order of the Fly, and the fought against Koshchei on his way to Pandemonium to meet Gamory. Later, after Koshchei was sucked dry off his blood by a demon and tossed into the Stygian sea of Hell, one of these angels swallowed him.
Koshchei managed to destroy the one that swallowed him after coming to term with his guilt and past then gaining the last bit of the Baba Yaga's magic as a gift from Vasilissa. The other angel was enraged and destroyed him, but Koshchei quickly regain his youthful body and obliterated that angel as well before collapsing from fatigued.