I just got why Geloe, from Memory, Sorrow and Thorn, has Baba Yaga references.
Because Geloe is this series' Gandalf equivalent (well, female Gandalf). And Gandalf was a wholly positive version of Odin. So Tad Williams searched for another ambiguous mythological character to take inspiration from for his witch, and he made her a positive Baba Yaga.
I see what you did there.
[Also, using this post to do a small advertisement for Memory, Sorrow and Thorn. If you are wondering how fiction evolved from Tolkien's Lord of the Rings to Martin's A Song of Ice and Fire, Tad Williams' "Memory, Sorrow and Thorn" is the answer.
As, on one side it was one of the main, if not THE main inspiration for ASoIaF - Martin himself said without Memory, Sorrow and Thorn there wouldn't be an ASoIaF today, and he took back a LOT of elements from it - evil fae of the cold winter from the north, evil red-clad priests wielding fire, the return of magic into a world torn apart by conflicts between contesters for the throne, dragons shaping the history of a feudal society...
And on the other side, Memory, Sorrow and Thorn was one of the two biggest and most famous "Tolkienesque fantasy" series of the 90s - alongside "The Wheel of Time". So this series is literaly the missing link between The Lord of the Ring (that it pays heavy homage and many references to, if not outright rewrites) and A Song of Ice and Fire.]
