Eustathius continued to waver among the varieties of Arianism, signing all manner of heretical and contradictory formulas of faith. In 385, he was [[deposition|deposed]] from the [[see]] of Sebaste by a synod at Melitene and succeeded by [[Meletius of Antioch|Meletius]], although his semi-Arian followers remained loyal to him. His deposition seemed not to effect his standing as he was asked by the semi-Arian bishops to be at their synod at Ancyra to oppose the spread of Anomoean doctrines. At the [[Council of Seleucia]] on [[September 27]], 359, Eustathius played a prominent place in the indecisive proceedings. He was among the group of bishops, who after the council, were sent to Constantinople to present their case before Emperor Constantius. Eustathius led their case against the Arians, presenting their formula of the the dissimilarity of the Father and Son, when the Arian delegation from the [[Council of Rimini]], to the liking of Constantius, announced their position proscribing the Homoousion formula. With this turn Eustathius and his party were compelled to agree which ended the council of which St. Jerome wrote: "The whole world groaned and was astonished to find itself Arian." <ref>Jerome, Dialogue Against the Luciferians, 19.</ref>

With the death of Constantius in 361, Eustathius and the other banished bishops were recalled by Emperor Julian. With his return, Eustathius immediately repudiated his signature on the creed of the Council of Rimini and the rejection of pure Arianism. As reported by Sozomen, Eustathius joined with others in a number of synods in which he condemned the supporters of Acacius, denounced the creed of the Rimini, and asserted that Homoiousion was the true formula over that of the Homoousion and the Anomoeon of Aetius and his followers. <ref>H. E. v. 14</ref>