Faraday Cage
I'm not sure I have the chops to write a TL, but just for discussion: what if a fourth Abrahamic religion came into prominence some time after the rise of Islam, but soon enough to carve out a sphere of influence and be part of medieval struggle between Christianity and Islam? Could some sort of heretical new sect take over the Byzantine Empire? Or maybe a new religion could arise in Persia before Islam could cross to there from Arabia? Or maybe contact with Christians and Muslims would create an Abrahamic but individual religion in the last pagan bastions of Eastern Europe/Eurasia?