In Legend, it's possible to gain more than one source of Fast Healing - such as, for example, having both the Path of Ancestors and Battle's Tempering tracks, or by successfully using the Vigor skill while in possession of the Cheerful Hemoglobin feat. I've scoured the relevant sections and cannot find a statement for or against this, so I ask this: do multiple sources of Fast Healing stack to create better healing?
Fast healing from multiple sources will stack.
page 200 "Fast Healing Some creatures have the extraordinary ability to heal very quickly, tagged as [Fast healing]. This ability always includes a number, such as “[Fast healing] 3”; a creature with this ability heals that number of hit points every [Round] at the beginning of its turn. The [Battered] condition negates healing from this source while it is active, although the healing resumes once the condition is gone."
It simply provides healing at the beginning of your turn, and so multiple instances of fast healing would mean you get healed multiple times. There is nothing that says only one will apply.