Tahmetianity, The Tahmetian Crusades
Tahmetianity is considered by many to be a scam; it was founded by the appearance of the same "prophet" in 1514 AT, on five different worlds at the edge of First Federation territory. This 'miracle' took many decades to confirm, as in the pre-wormhole period only light-speed messages could be sent between the worlds concerned.
This "miracle" caused a mass movement, a religion that gained the adherence of billions of people and seriously weakened Universalism, Christianity and Islam on these worlds (the multiple instances of this "prophet" claimed to be the messenger of Jehovah/Allah). On several worlds the Tahmetian-controlled governments persecuted and even massacred believers in other types of religions, including Etodists, Undyoists, Venpredessi (a movement of ancestor-worshippers), various neopagans and even Tahmetian heretic groups.
Undyoists claimed that Tahmetianity was an elaborate scam, its founders using some secretFaster-than-light technology to organize it and later claim power. But there was no FTL technology involved; eventually the Undyoist investigators discovered that Engenerator technology had been secretly utilised on each world to produce the multiple instances of the Prophet. This technology had been developed less than a hundred years before, and was in fairly common use within the Inner Sphere but was still almost unknown at the edge of colonised space.
In due course Tahmetian religion was thoroughly discredited by the efforts of Undyoist skeptics, and also became unpopular due to reports of atrocities in the Tahmetian worlds. Eventually the governments of the five worlds in question fell into disunion, attacking each other. One of the prophets was murdered by an antitheist resistance movement only to reappear alive a week later. The influence of transapients on the whole incident is debated. There are still hardcore followers of the faith, who remain very antithetical and hostile to Undyoists.