Ring of Catherine Summoning

Summons 1D6 Catherines for 4-8 hours duration.  Unknown number of charges remaining.  Catherines appear as a 19-year-old woman in a pretty blue dress. They are all LVL-0, HP-4, AC-10.  They have no discernible skills, but when they appear they will seem complacent and happy to help the summoner with anything reasonable.  They otherwise act like normal if unusually perky young women.  When the spell wears off, a Catherine will usually giggle and say "Oops!" before disappearing.