muszicman, that's all I ever said. God's character or nature is immutable, but his power stretches forth.
Certainly, as a first cause he moves things, but nothing moves God.
Council of Nicea decided against the arians who were saying Christ was mutable and therefore not God.
The Arian controversy related more to saying Christ was creature, not uncreated Creator. Its rejection of the Deity of Christ was the crux of the matter, not the exact understanding of immutability (even classical theologians are affirming weak vs strong immutability now).