The Blend nodes allow for combining mutiple texture layers. 



Blend



Figure 1: Octane Texture Layer - Blend Node List


The Layer Group nodes's Input socket will only accept Composite Texture Layer nodes, other Layer Group nodes, or any of the Composite Texture nodes (figure 2). Texture nodes found under the Octane Textures category must be connected to a Composite Texture Layer node before connecting to a Layer Group node (figure3). 



Layer Group



Figure 2: Nodes accepted by the Layer Group node



Composite Texture Layer



Figure 3: A Noise Texture connected to a Composite Texture Layer node