Like how the Mirror is the only way to Wonderland.
Right.
So if Red came via cyclone, then she’s coming from Oz, and not, say, Oz to EF/SB to the Underworld which seems to answer the question on whether or not the Underworld is for all worlds/realms and not just EF-character specific.
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"He was a lot of things to me" "The only conclusion was love"