[Mivereous]

If you contracted for

• Murai - lose murai equal to Youkai level*5.
  
• Stats - debuff the stat you were contracted with by 5 for Youkai level/10, minimum of 2, battles. (I.e., you were contracted by STR, lose 5 STR for X battles.)
  
• Item Rarity - they take a random item from your inventory when they leave OR (because people will moan about not knowing how to use a bank) decrease your encumbrance by Youkai level/10 for 24 IC hours.
  
• Meeting Another Youkai - the Youkai they were friends with is now sad they are gone, and cannot be summoned/installed for released-Youkai level/15, minimum of 1, battles.

Not sure if I missed any other ways of contract.