Call me old-fashioned, but my favorite fantasy mother is Grendel’s mom from the Anglo-Saxon epic Beowulf. The beast who bedeviled Beowulf had a mother, after all, who was as formidable as her son in many ways, and who reacted to the death of her child with all the ferocity you’d expect; and that asshole Beowulf goes after her, steals a sword from her own hoard, and chops her head off at the bottom of her lake! Right in her own house! She’s a tragic figure, really.
There’s a lot of debate, much of it coming down to tough-to-translate words from the source text, about whether Grendel’s mother was a monster on par with Grendel himself, or a powerful magical warrior woman or “water woman,” and she’s been depicted as a wily seductress (hell, she was played by the naked animated version of Angelina Jolie in a recent movie!) or dark goddess as often as a woolly monster. That ambiguity is part of what appeals to me, and what makes her character more complex and compelling than a simple poster child for historical misogyny.