The above item seems to have been missed in the book so the author posted this on a Facebook question:
"Ring of Transference – This ring may only be worn by a spellcaster. Once per game, the wearer of the ring can spend an action to transfer up to 5 points of their own Health to another member of their warband that is in line of sight, on a 1-for-1 basis. So, if the wearer spend 3 Health, they may transfer 3 Health to another warband member. This may not take the other warband member above their starting Health."