He does not tell us in Scripture that he determined to change his essential character. Rather, he tells us that he comes down, that he stoops, that he-while remaining himself essentially-assumes contingent properties in order to relate the things of his creation to himself. He is the initiator and preserver of this covenant relationship.
All of this is to say that it is God who has made compatible what would have otherwise remained incompatible (recall the Westminster Confession, 7.1). To put it in terms of SPC, there are two properties (or two sets of properties) that differ essentially. There are essential properties of God and essential properties of creation. These properties ties differ; they could even be said, perhaps, to be opposites. Thus, there are two entities, x_1 and x_2, creation and Creator, that appear to be incompatible... What unifying entity will supervene on x_1, and x_2 in such a way as to make them compatible without at the same time altering any of their essential properties? In a word, condescension; in two words, God's condescension.
It is God condescending, his act of condescension that, ipso facto, brings together the properties of Creator and creation in such a way as to preserve the essential properties of both, all the while placing them both within the same, unified, context. The unifying element, then, is covenant, the bringing together, by God, of the Eimi and the eikon. To put it in theological terms, the infinite gap that exists between God and creation is bridged by God's covenant condescension with respect to his creation.