Thomas Covenant, an embittered and cynical writer, afflicted with leprosy and shunned by society, is fated to become the heroic savior of the Land, an alternate world. In ten novels, published between 1977 and 2013, he struggles against Lord Foul, "the Despiser", who intends to escape the bondage of the physical universe and wreak revenge upon his arch-enemy, "the Creator". The Chronicles of Thomas Covenant - Wikipedia The original The Land? lol
I haven't read the Thomas Covenant books yet, but they're on my list now. Sounds like a very early example of portal fiction...