Blends between an undefined number of poses that can be added or removed from the node via the right-click context menu. By default, 2 poses are available, but this can be reduced down to 0. With 0 poses, it will just output the refpose. For each added pose to blend between, the node has an associated “Desired Alpha” input. By default, the alpha values on the node are normalized across all input alphas, but this can be turned off in the node details.

The node also has an undocumented “Additive Node” property. The only effect this property has, is the nodes behaviour when it has 0 input poses. In that case, this property defines whether the output of the node will be the regular RefPose or the AdditiveIdentity.