Raku
Essential Reiki	Serpent Variant

Raku is curently only used during attunements, during which it has two functions.   First, it facilitates opening up the new healer's energy channels, allow him to handle far larger flows of chi and other fundamental energies.   Second, it is used to separate the auras of the attuning master and the new healer.  

It seems likely there are other uses for Raku and the Reikifire Ministry encourages everyone to meditate on Raku and report any new information.