you can give healing items for Kris/use overheal on Kris to extend the 'timer' significantly
usually I'd defend turn 1 and 2, overheal turn 3, take the shadowmantle turn 4, and use festivemoss turn 5 to get both of their HP back up
probably use a bunkerration after the first [lower guard] and the spincake after the second, to keep Kris's HP up
this is not the first time people have had issues with the star attacks, I don't really get why people find them so difficult, but I might add an option to make those easier at some point if this many people struggle with them so much