Drainheart sword

The Master treasure named Drainheart sword has the keyword Absorb Stamina, but no (), I don’t find anything about this here or in the errata, is it a typo? Should be 1? Or do you get Stamina points back equal to all the damage caused?

The rules update in one of the card packs (I forget which one off the top of my head) gives you the answer, and it’s a bit of a retcon. If there is no rating for a keyword, you should consider it to be (1).