So... someone made a suggestion that the eikon in Eureka is Raiden. And no, that wouldn't be an Far Eastern kami associated with thunder... In FFVI, Raiden is the upgraded form of of the esper Odin. Yeah.

That would go a long way in explaining why Odin would have still been sealed in Urth's Fount at the time Galuf and Co. were sealing another eikon with a Zantetsuken-like blade in Baldesion.