Their rugged angles are soothed and freshened and embossed with green mosses, fresh life and decay mingling in pleasing measures.

In this context, "embossed" likely refers to the way the green mosses cover and adorn the rugged angles of the surfaces being described. It suggests that the mosses are not just present but are creating a distinct texture or pattern that enhances the appearance of those angles, giving them a more visually interesting and layered quality. The use of "embossed" implies an addition of depth and relief, highlighting the interplay between the natural elements of life (the moss) and the existing rugged features.