Imagine my surprise when I suddenly found myself watching pretty much the same story:
1) a three-sided war between three organizations, at least one of which is unaware of the participation of the third in the fight -
the DWMA, Arachnophobia, and Medusa's coven
SD-6, Irina Derevko's clique, and the CIA
2) the war consists of a series of fights over semi-magical tchotkes, literal mcguffins created by a long-dead, legendary da Vinci figure -
Eibon and his Magic Tools
Milo Rambaldi and his deranged series of artifacts
3) a horrible, Medea-like harridan of a mother, murderous, vicious, sociopathic and dreadfully manipulative, walks into the figurative front-office of the "good guys" faction, and surrenders, in order to embody the Hannibal in a cage trope -
Medusa the Younger, having survived her own evisceration & possessed a random child, thus protecting herself from the whole "thou shalt not suffer a witch to live" thing the DWMA has going by hiding inside her body-hostage; this after a half-dozen episodes of manipulating her seriously disturbed woobie of a son Crona from the shadows into betraying that faction
Irina Derevko, who after shooting her estranged daughter and then her own Dragon in the opening episode of the season, apparently decides that it'd be more fun to screw with the CIA from inside of a deeply buried jail cell than from within the nominally safe confines of her own faction
They both have peculiar, attraction-repulsion relationships with core figures within the "good guys" organizations, Medusa with the hanging-onto-sanity-with-his-fingertips Dr. Stein, and Irina with her estranged husband, Jack Bristow.
These are terrifying mother-figures - unloving, unblinking and menacing. Medusa had a child for the express purpose of moulding it into a science experiment, denying it love and affirmation & infecting it with a species of madness to see if she could breed a "Kishin" - sort of an evil god. Irina had a child for the sole purpose of cementing her role as a loving wife & mother to a CIA agent and his child, and seems entranced by the strange creature from her long-past stint as a sleeper agent & assassin; the first thing she does upon being reunited with her daughter is to muse about how easily she could have killed her in infancy. Both characters are expressions of the vulnerability of children in the hands of their mothers, and the potential for what some wags have called "retroactive abortion". They're avatars of Kali - the killing-mother who brought you into this world and could quite easily take you out of it again.